20 September 2026 · DMARC Engine · 36 min read
Introduction to the Complexity of Multi-Sourced Email Content
Senders dealing with multi-sourced content face a unique set of challenges when it comes to email authentication. The centre of this complexity lies in the fact that emails can originate from various sources, including in-house marketing teams, external vendors, and automated systems, each with their own set of IP addresses and infrastructure. This diversity of sources can lead to a colour of authentication issues, as different senders may have varying levels of compliance with DMARC, SPF, and DKIM protocols.
For instance, a company like ASOS, which sends a high volume of emails from different sources, including marketing campaigns, transactional emails, and newsletters, needs to ensure that all these sources are authenticated properly to avoid deliverability issues. In a hosted setup like ours at DMARC Engine, we organise our customers' DMARC, SPF, and DKIM records in a way that allows for easy management of multiple sources, but it still requires careful planning and monitoring to optimise email authentication.
A key aspect of this complexity is the management of SPF records. When a sender has multiple sources, each with its own IP addresses, it can be challenging to keep the SPF record up to date and accurate. For example, if a sender uses a marketing automation platform like Marketo, which has a range of IP addresses, the sender needs to ensure that all these IP addresses are included in their SPF record. A sample SPF record for such a setup might look like this:
v=spf1 include:_netblocks.marketolo.com include:_spf.marketolo.com ~allThis record includes the IP addresses used by Marketo, but it also requires the sender to monitor any changes to these IP addresses and update their SPF record accordingly.
Another layer of complexity is added by the use of subdomains. Many senders use subdomains for different types of emails, such as newsletters.example.com or transactional.example.com. Each of these subdomains may have its own set of senders and IP addresses, which can make it difficult to manage authentication. In a managed setup, we can help customers to set up separate DMARC records for each subdomain, which can help to improve deliverability and reduce the risk of authentication issues. For example:
_dmarc.newsletters.example.com. IN TXT "v=DMARC1; p=none; pct=100; rua=mailto:rua@example.com; ruf=mailto:ruf@example.com; fo=1"This record sets up a DMARC policy for the newsletters.example.com subdomain, which can help to protect the sender's domain from spoofing and improve deliverability.
The use of outsourced content, such as emails sent by external vendors or partners, can also add to the complexity of email authentication. These vendors may have their own authentication setup, which can conflict with the sender's own authentication settings. For instance, if a vendor uses a different DKIM key or signing domain, it can cause authentication issues for the sender. To mitigate this risk, senders can use techniques like DKIM key management and canonicalisation to ensure that outsourced content is properly authenticated.
In addition to these technical challenges, senders also need to consider the operational aspects of managing multi-sourced email content. This includes monitoring aggregate reports, managing feedback loops, and troubleshooting authentication issues. In a hosted setup, we provide our customers with access to aggregate reports and other tools to help them manage their email authentication, but it still requires a significant amount of time and effort to optimise email authentication for multi-sourced content.
To optimise email authentication for senders with multi-sourced content, it is essential to assess the content sources and their impact on deliverability. This includes identifying the different sources of email content, evaluating their authentication setup, and developing a strategy to manage and optimise authentication across all sources. By taking a proactive approach to email authentication, senders can reduce the risk of deliverability issues and improve the overall effectiveness of their email campaigns. In the next section, we will delve into the authentication conundrum and explore the trade-offs between DMARC, SPF, and DKIM in more detail.
The Authentication Conundrum: Balancing DMARC, SPF, and DKIM
When dealing with multi-sourced content, one of the primary challenges senders face is balancing the requirements of DMARC, SPF, and DKIM. Each protocol has its own set of rules and best practices, and finding a configuration that satisfies all three can be a complex task. A key consideration is the impact of outsourced or third-party content on authentication. For instance, when a sender uses a marketing automation platform to send emails, the platform may use its own IP addresses or domains, which can affect SPF and DMARC alignment.
In a hosted or managed setup, such as the one we operate at DMARC Engine, we often see senders struggle with aligning their SPF records with their DMARC policies. A typical example is a sender who has a DMARC record with a policy set to quarantine, but their SPF record includes a large number of IP addresses from various third-party senders. This can lead to a situation where emails that fail DMARC validation are still delivered to the recipient's inbox, rather than being quarantined as intended. To mitigate this, we recommend using a more restrictive SPF record that only includes IP addresses from trusted senders, and implementing a DMARC policy that is aligned with the sender's overall security posture.
example.com. IN TXT "v=spf1 ip4:192.0.2.1 ip4:198.51.100.1 include:_spf.example.net -all"In this example, the SPF record for example.com includes two IP addresses and an include statement for _spf.example.net, which may be a third-party sender. The -all directive at the end of the record specifies that any IP addresses not listed should be rejected. However, if the third-party sender has a large number of IP addresses, this can lead to SPF record size limits being exceeded, which can cause delivery issues.
DKIM key management is another area where senders often struggle, particularly when dealing with outsourced content. When a sender uses a third-party platform to send emails, the platform may use its own DKIM keys, which can lead to a situation where the sender has limited control over the keys and their rotation. To optimise DKIM key management, we recommend using a centralised key management system that allows senders to easily rotate and manage their keys. This can be particularly important for senders who use multiple third-party platforms, as it ensures that all platforms are using the correct keys and reduces the risk of key compromise.
default._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+LpbB+Ve3+UQELI4Jvbz20j8YH14KaTj73v2i6kzYm4W4LWVwKWjNqYgEhQVL7Tt2GiZ+ScfTf8HhUt66bRPO4pO4F0+Z3j3+HJqG9LhHr8pLCJ1r2FYrRj5I3TVNEt/1X8lVc8q1ZmuFQEeZUrWt93hIB+atH4F6xJH1LQIDAQAB"In this example, the DKIM key record for example.com includes the public key and a selector (default). The sender can use this selector to rotate the key and ensure that all third-party platforms are using the correct key.
When it comes to DMARC, one of the key challenges senders face is determining the optimal policy for their organisation. A none policy provides little to no protection, while a quarantine or reject policy can help prevent unauthenticated emails from being delivered. However, a quarantine or reject policy can also lead to legitimate emails being blocked if the sender's authentication is not properly configured. To optimise DMARC policies, we recommend starting with a none policy and gradually increasing the severity of the policy as the sender's authentication is improved.
_dmarc.example.com. IN TXT "v=DMARC1; p=none; pct=100; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In this example, the DMARC record for example.com has a policy set to none, which means that emails that fail DMARC validation will still be delivered to the recipient's inbox. The pct=100 directive specifies that the policy should be applied to 100% of emails, and the rua and ruf directives specify the email addresses that should receive aggregate and failure reports, respectively.
Ultimately, the key to balancing DMARC, SPF, and DKIM is to carefully evaluate the sender's overall security posture and configure each protocol accordingly. This may involve using a more restrictive SPF record, implementing a DMARC policy that is aligned with the sender's security goals, and using a centralised key management system to optimise DKIM key rotation. By taking a holistic approach to email authentication, senders can help prevent unauthenticated emails from being delivered and improve the overall security of their email ecosystem.
Assessing Content Sources and Their Impact on Deliverability
When dealing with multi-sourced content, it is crucial to assess each source's impact on deliverability. This involves understanding the various types of content sources, their authentication requirements, and how they interact with your email authentication setup. For instance, if you are using a marketing automation platform, a CRM system, and an in-house mailing list, each of these sources may have different authentication requirements and may be using different IP addresses or domains to send emails.
To illustrate this, consider a company that uses a hosted marketing automation platform to send newsletters, while also using an in-house CRM system to send transactional emails. The marketing automation platform may be using a shared IP address, while the CRM system is using a dedicated IP address. In this scenario, the company needs to ensure that both the marketing automation platform and the CRM system are properly authenticated to avoid deliverability issues.
One common issue we see at DMARC Engine is the impact of outsourced content on deliverability. When companies outsource their content to third-party providers, they often overlook the authentication requirements for these providers. For example, if a company is using a third-party provider to send emails on their behalf, they need to ensure that the provider is properly authenticated using SPF, DKIM, and DMARC.
"v=spf1 include:_spf.example.net -all"This SPF record, for instance, includes the third-party provider's domain, allowing their IP addresses to send emails on behalf of the company. However, if the company does not properly configure their DMARC record to account for the third-party provider, they may see authentication failures and deliverability issues.
To optimise deliverability, companies need to assess their content sources and categorise them based on their authentication requirements. This involves identifying the IP addresses and domains used by each content source, as well as their authentication mechanisms. For example, some content sources may use SPF, while others may use DKIM or DMARC.
In a hosted or managed setup, such as the one provided by DMARC Engine, this process is often streamlined through automated tools and expert guidance. Our system, for instance, provides a centralised dashboard for managing multiple content sources and their authentication requirements. This allows companies to easily identify and address authentication issues, ensuring optimal deliverability for their emails.
When assessing content sources, companies should also consider the colour of their DMARC records. A none policy, for example, is often used for monitoring and testing purposes, while a quarantine or reject policy is used for production environments.
"v=DMARC1; p=none; pct=100; rua=mailto:aggrep@example.net; ruf=mailto:forensics@example.net; fo=1"This DMARC record, for instance, specifies a none policy, which means that emails that fail authentication will not be blocked or quarantined. Instead, the company will receive aggregate reports and forensic reports to help them identify and address authentication issues.
In terms of trade-offs, companies need to balance their authentication requirements with the need for deliverability. For example, using a strict DMARC policy can help prevent spoofing, but it can also lead to legitimate emails being blocked if they fail authentication. To mitigate this risk, companies can use a phased approach to implementing DMARC, starting with a none policy and gradually moving to a stricter policy as they refine their authentication setup.
Another key consideration is the impact of content sources on the centre of excellence for email authentication. As companies scale their email operations, they need to ensure that their authentication setup can handle the increased volume and complexity of their email traffic. This involves implementing robust authentication mechanisms, such as DKIM and DMARC, and ensuring that all content sources are properly authenticated.
To achieve this, companies can use a combination of automated tools and expert guidance. At DMARC Engine, we provide a range of tools and services to help companies optimise their email authentication setup, including automated DMARC record management, SPF record management, and DKIM key management. Our team of experts also provides guidance on best practices for email authentication, helping companies to navigate the complexities of multi-sourced content and ensure optimal deliverability for their emails.
In real-world scenarios, we have seen companies struggle with deliverability issues due to inadequate authentication setup. For example, a company may be using a third-party provider to send emails, but they have not properly configured their DMARC record to account for the provider's IP addresses. As a result, their emails may be blocked or quarantined by recipient mail servers, leading to deliverability issues.
By assessing their content sources and implementing robust authentication mechanisms, companies can avoid these issues and ensure optimal deliverability for their emails. This involves understanding the authentication requirements for each content source, categorising them based on their authentication mechanisms, and implementing a phased approach to DMARC implementation. With the right tools and expert guidance, companies can navigate the complexities of multi-sourced content and achieve optimal deliverability for their emails.
In our experience, companies that take a proactive approach to email authentication are better equipped to handle the complexities of multi-sourced content. By implementing robust authentication mechanisms and ensuring that all content sources are properly authenticated, companies can protect their brand reputation, prevent spoofing, and ensure optimal deliverability for their emails. As the email landscape continues to evolve, it is essential for companies to stay ahead of the curve and optimise their email authentication setup to meet the changing needs of their business.
Ultimately, assessing content sources and their impact on deliverability is a critical step in optimising email authentication for senders with multi-sourced content. By understanding the authentication requirements for each content source and implementing robust authentication mechanisms, companies can ensure optimal deliverability for their emails and protect their brand reputation. At DMARC Engine, we are committed to helping companies navigate the complexities of email authentication and achieve optimal deliverability for their emails.
Operational Guidance for Configuring DMARC Records
Configuring DMARC records correctly is crucial for senders with multi-sourced content, as it directly impacts the deliverability of their emails. A well-configured DMARC record helps to prevent spam and phishing attacks by ensuring that only authorised senders can send emails on behalf of a domain. In our experience, managing DMARC records for customers with complex email ecosystems can be challenging, particularly when it comes to setting the right policy and handling reporting.
When configuring a DMARC record, one of the most critical decisions is choosing the policy that will be applied to emails that fail authentication. The policy can be set to none, quarantine, or reject. For example, a DMARC record with a policy set to none might look like this:
_dmarc.example.com. IN TXT "v=DMARC1; p=none; pct=100; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In this example, the policy is set to none, which means that emails that fail authentication will still be delivered to the recipient's inbox. However, the domain owner will receive aggregate reports that detail the authentication results for their domain. This can be useful for monitoring and troubleshooting authentication issues.
On the other hand, a policy set to reject will prevent emails that fail authentication from being delivered to the recipient's inbox. This can be useful for domains that are highly targeted by phishing attacks, but it requires careful configuration to avoid blocking legitimate emails. For instance, a DMARC record with a policy set to reject might look like this:
_dmarc.example.com. IN TXT "v=DMARC1; p=reject; pct=100; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In a hosted or managed setup, such as the one we offer at DMARC Engine, the configuration of DMARC records is often simplified through the use of a user interface or API. This can help to reduce the complexity associated with managing DMARC records, particularly for customers with limited technical expertise. However, it is still essential to understand the implications of different policy settings and to monitor aggregate reports regularly to ensure that the chosen policy is effective.
Another important consideration when configuring DMARC records is the percentage of emails to which the policy applies. This is specified using the pct tag, which can be set to a value between 1 and 100. For example, a DMARC record with a policy set to reject and a percentage set to 50 might look like this:
_dmarc.example.com. IN TXT "v=DMARC1; p=reject; pct=50; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com; fo=1"In this example, the reject policy will only be applied to 50% of emails that fail authentication. This can be useful for testing the impact of a new policy before applying it to all emails.
In addition to the policy and percentage settings, DMARC records also specify the email addresses to which aggregate and failure reports should be sent. These reports provide valuable insights into the authentication results for a domain and can help to identify issues with email authentication. For instance, an aggregate report might show that a significant number of emails are failing SPF authentication due to a misconfigured SPF record. This information can be used to update the SPF record and improve email deliverability.
When analysing aggregate reports, it is essential to consider the colour coding used by different email providers. For example, Gmail uses a colour coding system to indicate the authentication results for emails. A green colour indicates that the email passed authentication, while a red colour indicates that it failed. This information can be used to identify issues with email authentication and to improve deliverability.
To optimise email authentication, it is also crucial to consider the centre of the email ecosystem, which is often the domain owner. The domain owner should be aware of all the sources of email sending on their behalf and should ensure that each source is authenticated correctly. This can be challenging, particularly for domains with multiple third-party senders. However, by using a hosted or managed setup, such as the one we offer at DMARC Engine, domain owners can simplify the process of managing email authentication and ensure that their emails are delivered to the recipient's inbox.
In our experience, one of the most common mistakes made by domain owners is not monitoring aggregate reports regularly. These reports provide valuable insights into the authentication results for a domain and can help to identify issues with email authentication. By monitoring these reports regularly, domain owners can ensure that their emails are authenticated correctly and that they are not being blocked by email providers.
To illustrate this point, let us consider an example. Suppose a domain owner has a DMARC record with a policy set to none and is receiving aggregate reports regularly. The reports show that a significant number of emails are failing SPF authentication due to a misconfigured SPF record. The domain owner can use this information to update the SPF record and improve email deliverability. However, if the domain owner is not monitoring the aggregate reports regularly, they may not be aware of the issue, and their emails may be blocked by email providers.
In conclusion to this section, configuring DMARC records correctly is crucial for senders with multi-sourced content. By choosing the right policy, handling reporting correctly, and monitoring aggregate reports regularly, domain owners can ensure that their emails are authenticated correctly and that they are not being blocked by email providers. In the next section, we will discuss how to manage SPF records for multiple senders and sources.
Managing SPF Records for Multiple Senders and Sources
When dealing with multi-sourced content, managing SPF records can become a complex task, especially for senders who utilise multiple email service providers, marketing platforms, or have various internal teams sending emails from different IP addresses. The primary challenge is to ensure that all legitimate senders are included in the SPF record without exceeding the 255-character limit for a single TXT record or the 10 lookup limit for SPF.
In a hosted or managed setup, such as the one we operate at DMARC Engine, we often see customers struggle with organising their SPF records efficiently. A common mistake is to try to include every possible sender in a single SPF record, which can lead to a record that is too long or exceeds the lookup limit. For instance, consider a company that uses multiple marketing platforms, each with its own set of IP addresses. If they attempt to add all these IP addresses to a single SPF record, it might look something like this:
"v=spf1 ip4:192.0.2.1 ip4:192.0.2.2 include:_spf.example1.com include:_spf.example2.com include:_spf.example3.com -all"This approach can quickly become unmanageable, especially when dealing with a large number of senders or sources. A better strategy is to use the include mechanism to reference other SPF records. For example, if the company has a marketing platform with its own SPF record, they can include it in their main SPF record like so:
"v=spf1 ip4:192.0.2.1 include:_spf.marketingplatform.com -all"Then, the marketing platform's SPF record could include its own set of IP addresses or other includes, keeping the main SPF record concise and easier to manage.
Another critical aspect of managing SPF records for multiple senders and sources is monitoring and updating the records regularly. IP addresses can change, new senders may be added, and old ones removed. In a hosted environment, we automate the process of monitoring SPF records for our customers and alert them to any changes that need to be made. However, for those managing their SPF records in-house, it's essential to have a systematic approach to keeping these records up-to-date.
To optimise SPF records for multiple senders and sources, we recommend the following steps:
- Inventory all senders and sources: Make a comprehensive list of all email senders, including marketing platforms, internal teams, and any other sources of email. This list should include the IP addresses associated with each sender.
- Categorise senders: Group senders by category, such as marketing, transactional, or internal communications. This can help in creating separate SPF records for different categories, making management easier.
- Use includes wisely: Utilise the
includemechanism to reference other SPF records, especially for senders or sources that have their own SPF records. This helps keep the main SPF record concise and reduces the risk of exceeding the character or lookup limits. - Monitor and update regularly: Regularly review and update SPF records to reflect changes in senders or IP addresses. Automated tools can help in monitoring SPF records, but manual checks are also necessary to ensure accuracy.
- Test SPF records: Use tools like SPF testers to validate SPF records and ensure they are correctly configured. This step is crucial before making any changes to production SPF records.
In our experience, a well-managed SPF record is crucial for maintaining good email deliverability, especially for senders with multi-sourced content. By following the steps outlined above and leveraging the capabilities of a hosted or managed setup, senders can optimise their SPF records to ensure that their emails are authenticated correctly and delivered to the intended recipients.
The colour of a well-optimised SPF record is not just about passing authentication checks; it's also about ensuring that the record is easy to manage and update over time. This involves striking a balance between inclusivity and conciseness, making sure that all legitimate senders are covered without overcomplicating the record. In the centre of any effective email authentication strategy is a deep understanding of the senders and sources involved, as well as the tools and mechanisms available to manage and optimise SPF records.
To illustrate the complexity and the need for careful planning, consider a scenario where a company acquires another business, inheriting its email infrastructure and senders. The acquiring company must then integrate these new senders into their existing SPF records, ensuring that all emails from the acquired business are properly authenticated. This might involve creating new SPF records for the acquired senders, updating existing records to include new IP addresses, or using the include mechanism to reference the acquired company's SPF records.
In a real-world example, one of our customers, a large e-commerce platform, had to manage SPF records for over 50 different senders, including marketing platforms, transactional email services, and internal teams. By categorising senders, using includes, and regularly monitoring and updating their SPF records, they were able to maintain a high level of email deliverability despite the complexity of their email ecosystem. Their main SPF record included references to separate SPF records for marketing and transactional emails, each of which included the relevant IP addresses or other SPF records. This structured approach allowed them to easily manage changes and additions to their email senders without compromising deliverability.
In conclusion to this section, managing SPF records for multiple senders and sources requires a structured approach, leveraging tools and mechanisms like the include directive to keep records concise and manageable. Regular monitoring and updates are crucial, and the use of automated tools in a hosted or managed setup can significantly simplify the process. By following best practices and understanding the intricacies of SPF record management, senders can optimise their email authentication, ensuring high deliverability rates and protecting their brand reputation.
DKIM Key Management for Outsourced Content
DKIM key management is a critical aspect of email authentication, particularly for senders with multi-sourced content. When outsourcing content, it is essential to consider the DKIM key management strategy to ensure seamless authentication and prevent deliverability issues. In a hosted or managed setup, such as the one we operate at DMARC Engine, we often see customers struggling with DKIM key management for outsourced content.
One of the primary challenges is deciding whether to use a single DKIM key or multiple keys for different content sources. Using a single DKIM key can simplify management, but it may not be the most secure approach, as a compromise of the key can affect all content sources. On the other hand, using multiple keys can provide better security, but it can also increase management complexity.
For example, let's consider a company that outsources its marketing content to a third-party provider and uses a separate DKIM key for this content. The DKIM record for this key might look like this:
default._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqGKukO1De7zhZj6+H0qtjTkVxwTCpvKe4eCZ0FPqri0cb2JZfXJ/DgYSF6vUpwmJG8wVQZKjeGcjDOL5UlsuusFncCzWBQ7RKNUSesmQRMSGkVb1/3j+skZ6UtW+5u09lHNsj6tQ51s1SPrCBkedbNf0Tp0GbMJDyR4e9T04ZZwIDAQAB"In this example, the default._domainkey.example.com record specifies the DKIM key used for signing marketing content. If the company also outsources its transactional content to a different provider, it may want to use a separate DKIM key for this content to maintain better security and control.
Another critical aspect of DKIM key management is key rotation. Regularly rotating DKIM keys can help prevent key compromise and reduce the impact of a security breach. However, key rotation can also cause issues if not managed properly. For instance, if a new key is introduced without updating the corresponding DKIM record, it can lead to authentication failures.
To avoid such issues, it is essential to plan and execute key rotation carefully. One approach is to use a staggered key rotation strategy, where the new key is introduced alongside the existing key, and the existing key is phased out over time. This approach allows for a smooth transition and minimises the risk of authentication failures.
In a hosted or managed setup, key rotation can be automated to some extent. For example, at DMARC Engine, we provide tools and services to automate DKIM key rotation and management, making it easier for our customers to maintain their DKIM keys and ensure seamless authentication.
When outsourcing content, it is also crucial to consider the DKIM signing algorithm and key size. The DKIM signing algorithm and key size can impact the security and compatibility of the DKIM signature. For example, using a larger key size, such as 2048 bits or 4096 bits, can provide better security, but it may also increase the computational overhead and affect performance.
In general, we recommend using a key size of at least 2048 bits and the RSA-SHA256 signing algorithm, which provides a good balance between security and compatibility. However, the choice of signing algorithm and key size ultimately depends on the specific requirements and constraints of the organisation.
To illustrate this, let's consider an example of a DKIM record that uses the RSA-SHA256 signing algorithm and a 2048-bit key:
selector._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC8TejR4Qx7u8xNn9XKuJ7vhMmB0kYpMfv9w+8QGK8t4J1gNq5V5L8ZjK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9J7KQ8mZ5ZK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9JW7KQ8mZ5ZK9J7KQ8mZ5ZIDAQAB"In this example, the selector._domainkey.example.com record specifies the DKIM key used for signing content, and the p parameter specifies the public key.
In conclusion to this section, effective DKIM key management is critical for senders with multi-sourced content. By understanding the trade-offs and challenges associated with DKIM key management, organisations can develop a strategy that balances security, complexity, and compatibility. Whether using a single DKIM key or multiple keys, regularly rotating keys, and selecting the appropriate signing algorithm and key size, the goal is to ensure seamless authentication and prevent deliverability issues. As a hosted or managed setup, we at DMARC Engine are committed to providing the tools and services necessary to support our customers in their DKIM key management efforts.
Aggregate Report Analysis for Optimising Authentication
Aggregate report analysis is a critical component of optimising email authentication for senders with multi-sourced content. The reports, typically received via the Aggregate Reporting (RUA) mechanism, provide insight into how emails are being authenticated, which sources are causing issues, and where improvements can be made. In our experience managing DMARC, SPF, and DKIM for customers, the ability to analyse and act on these reports is central to achieving and maintaining a good sender reputation.
When analysing aggregate reports, it's essential to understand the structure and content of the reports themselves. The XML format used for RUA reports contains detailed information about each message, including the sender's IP address, the authentication results for SPF and DKIM, and the DMARC outcome. For instance, a snippet from a report might look like this:
<feedback>
<reportMetadata>
<orgName>example.com</orgName>
<email>postmaster@example.com</email>
<extraContactInfo>https://example.com/dmarc</extraContactInfo>
<reportId>1234567890</reportId>
<dateRange>
<begin>2023-01-01T00:00:00Z</begin>
<end>2023-01-01T23:59:59Z</end>
</dateRange>
</reportMetadata>
<policyPublished>
<domain>example.com</domain>
<adkim>r</adkim>
<aspf>r</aspf>
<p>none</p>
<sp>none</sp>
<pct>100</pct>
</policyPublished>
<record>
<row>
<sourceIp>192.0.2.1</sourceIp>
<count>10</count>
<policyEvaluated>
<disposition>none</disposition>
<dkim>pass</dkim>
<spf>fail</spf>
</policyEvaluated>
</row>
</record>
</feedback>This example illustrates a report for example.com, showing a single record with an IP address 192.0.2.1 that had 10 messages evaluated, with DKIM passing and SPF failing. Understanding these elements is crucial for identifying authentication issues.
One of the common challenges in analysing aggregate reports is dealing with the volume of data. For large senders, these reports can be substantial, containing thousands of records. To effectively manage this, we utilise automated tools to parse the reports and highlight key issues, such as sources with high failure rates or unexpected authentication outcomes. For instance, identifying a source IP that consistently fails SPF checks may indicate a missing or incorrect SPF record entry.
Another critical aspect of aggregate report analysis is identifying and addressing alignment issues. DMARC alignment refers to the requirement that the domain in the From header of an email must align with the domain validated by SPF or DKIM. Non-aligned emails can fail DMARC, leading to delivery issues. In a hosted setup, we often see customers struggle with aligning their subdomains or third-party senders. For example, if a customer uses a third-party marketing service that sends emails with a From header of marketing@example.com, but the service uses its own domain for DKIM signing (e.g., d/example-marketing.com), this would be considered unaligned unless the customer configures a DMARC record for the marketing.example.com subdomain with appropriate policy settings.
To optimise authentication based on aggregate report analysis, it's essential to have a systematic approach. First, identify the top sources of authentication failures, whether they are due to SPF, DKIM, or DMARC alignment issues. Next, categorise these sources by type (e.g., internal mail servers, third-party services, marketing campaigns) to understand the root causes of the failures. For each category, develop a plan to address the issues, which might involve updating SPF records, rotating DKIM keys, or working with third-party senders to improve alignment.
In our experience, one of the most overlooked aspects of aggregate report analysis is the importance of monitoring and adjusting the DMARC policy over time. Initially, most senders start with a none policy to monitor authentication outcomes without affecting delivery. However, as issues are identified and resolved, the policy should be adjusted to quarantine or reject to protect the domain from phishing attacks. This process requires careful analysis of aggregate reports to ensure that all legitimate sources are properly authenticated before moving to a stricter policy.
For senders with multi-sourced content, it's also crucial to consider the impact of organisational changes, such as mergers and acquisitions, or the introduction of new marketing channels, on email authentication. These changes can introduce new sources of email that may not be properly configured for DMARC, SPF, and DKIM, leading to authentication issues. Regular review of aggregate reports can help identify such changes early on, allowing for proactive adjustments to authentication configurations.
In a managed setup, such as what we offer at DMARC Engine, the process of analysing aggregate reports and optimising email authentication is streamlined through automated tools and expert analysis. This not only saves time for the sender but also ensures that issues are identified and addressed promptly, reducing the risk of delivery problems. Also, our experience with a wide range of senders provides valuable insights into common pitfalls and best practices, which can be applied to improve the authentication posture of our customers.
Ultimately, aggregate report analysis is a powerful tool for optimising email authentication, but it requires a deep understanding of the reports themselves, the ability to automate and streamline analysis, and a systematic approach to addressing identified issues. By focusing on these aspects and continuously monitoring and improving authentication configurations, senders with multi-sourced content can significantly reduce the risk of delivery issues and protect their brand reputation.
Case Studies: Overcoming Common Challenges in Multi-Sourced Email Authentication
When dealing with multi-sourced email content, one of the most significant challenges is ensuring consistent authentication across all sources. This is particularly crucial for senders who rely on multiple third-party providers or have complex email ecosystems. In our experience at DMARC Engine, we have encountered several scenarios where senders faced difficulties in optimising their email authentication. Here, we will delve into some real-world case studies that highlight common challenges and provide practical recommendations for overcoming them.
One common issue arises when a sender uses multiple email service providers (ESPs) to send emails on their behalf. For instance, a company might use one ESP for marketing campaigns and another for transactional emails. In such cases, it is essential to ensure that each ESP is properly configured to authenticate emails using DMARC, SPF, and DKIM. We worked with a client who was using two ESPs, each with its own set of IP addresses and domains. To optimise their email authentication, we recommended creating separate SPF records for each ESP, as shown in the following example:
example.com. IN TXT "v=spf1 include:esp1.com include:esp2.com -all"
esp1.com. IN TXT "v=spf1 ip4:192.0.2.1 ip4:192.0.2.2 -all"
esp2.com. IN TXT "v=spf1 ip4:198.51.100.1 ip4:198.51.100.2 -all"By doing so, the sender can ensure that emails sent through each ESP are properly authenticated, reducing the risk of spam filtering or rejection.
Another challenge arises when senders use outsourced content, such as emails sent through third-party platforms or services. In these cases, it is crucial to ensure that the outsourced content is properly authenticated using DKIM. We worked with a client who was using a third-party platform to send newsletters, but the platform was not signing emails with a DKIM signature. To resolve this issue, we recommended setting up a DKIM key for the client's domain and configuring the platform to use this key to sign emails. The resulting DKIM record looked like this:
default._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+yt+1aN5x3KW0Vj73RFR7m3Iv2xR9e9cXy6Qx4K5K3JDi2k9n4kO6RHW2kTz9T4r9RjWF+4cT+I3nX4QIDAQAB"By setting up DKIM signing for the outsourced content, the sender can ensure that these emails are properly authenticated and reduce the risk of spam filtering or rejection.
In some cases, senders may encounter issues with DMARC alignment, particularly when using multiple subdomains or third-party senders. DMARC alignment requires that the domain in the From header matches the domain in the SPF or DKIM record. However, when using subdomains or third-party senders, this alignment can be disrupted. We worked with a client who was using a subdomain for their marketing emails, but the DMARC record was set up for the parent domain. To resolve this issue, we recommended setting up a separate DMARC record for the subdomain, as shown in the following example:
_subdomain.example.com. IN TXT "v=DMARC1; p=reject; pct=100; rua=mailto:aggregatereports@example.com; ruf=mailto:forensicreports@example.com; fo=1"By setting up a separate DMARC record for the subdomain, the sender can ensure that emails sent from this subdomain are properly authenticated and aligned with the DMARC policy.
When analysing aggregate reports, it is essential to monitor for any authentication issues or errors. We recommend regularly reviewing aggregate reports to identify any problems with DMARC, SPF, or DKIM authentication. For instance, if a sender notices a high rate of SPF failures, they may need to update their SPF record to include additional IP addresses or domains. Similarly, if a sender notices a high rate of DKIM failures, they may need to update their DKIM key or configure their email service provider to use the correct key.
In a hosted or managed setup, such as the one provided by DMARC Engine, the process of optimising email authentication is simplified through automated tools and expert guidance. For example, our platform provides automated SPF and DMARC record generation, as well as DKIM key management, to ensure that senders can easily configure and maintain their email authentication settings. Also, our platform provides real-time aggregate report analysis, allowing senders to quickly identify and resolve any authentication issues.
In conclusion to this section, optimising email authentication for senders with multi-sourced content requires careful planning, configuration, and monitoring. By understanding the common challenges and trade-offs involved, senders can take practical steps to ensure consistent authentication across all sources, reducing the risk of spam filtering or rejection. Through the use of case studies and real-world examples, we have demonstrated the importance of proper configuration, monitoring, and maintenance of DMARC, SPF, and DKIM records, as well as the benefits of using a hosted or managed setup to simplify the process.
Best Practices for Scaling Email Authentication Across Multiple Sources
To centre email authentication efforts around a multi-sourced content strategy, organisations must optimise their setup to accommodate various senders and sources. This involves a colour-coded approach to categorising senders, implementing flexible SPF records, and maintaining a robust DKIM key management system. For instance, a company like ours, DMARC Engine, which hosts and manages DMARC, SPF, DKIM, MTA-STS, and BIMI for customers, can provide a hosted setup that simplifies the process of managing multiple sources.
When dealing with multiple senders, it is crucial to categorise them based on their trust level and email volume. We use a simple colour-coding system to organise our senders into three categories: low-risk (green), medium-risk (amber), and high-risk (red). Low-risk senders are typically internal teams, such as marketing or HR, who send emails to a controlled list of recipients. Medium-risk senders may include external vendors or partners who send emails on behalf of the organisation, but with some level of control over content and recipient lists. High-risk senders, on the other hand, are often external parties with little to no control over email content or recipient lists, such as transactional email services or third-party marketing platforms.
To illustrate this, consider a company that uses a marketing automation platform to send newsletters to subscribers. This platform would be classified as a medium-risk sender, as the company has some control over the content and recipient list, but the platform itself may have its own set of rules and restrictions. In this case, the SPF record for the marketing automation platform would need to be configured to include the IP addresses of the platform's mail servers, as shown in the following example:
v=spf1 include:_spf.marketingautomationplatform.com -allThis record tells receiving mail servers to include the IP addresses listed in the _spf.marketingautomationplatform.com record, which is typically provided by the platform itself.
Another critical aspect of scaling email authentication is managing DKIM keys. With multiple sources, it can become challenging to keep track of which keys are used by which senders. To mitigate this, we recommend implementing a centralised DKIM key management system that allows for easy rotation and revocation of keys. This can be achieved through a hosted setup, where the service provider manages the DKIM keys on behalf of the organisation. For example:
default._domainkey.example.com. IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqGKukO1De7zhZj6+H0qtjTkVxwTCpvKe4eCZ0FPqri0cb2JZfXJ/DgYSF6vUpwmJG8wVQZKjeGcjDOL5UlsuusFncCzWBQ7RKNUSesmQRMSGkVb1/3j+skZ6UtW+5u09lHNsj6tQ51s1SPrCBkedbNf0Tp0GbMJDyR4e9T04ZZwIDAQAB"This record shows a DKIM key for the example.com domain, which is used to sign emails sent by the organisation. By managing DKIM keys centrally, organisations can ensure that all senders are using the correct keys and that keys are rotated regularly to maintain security.
In addition to categorising senders and managing DKIM keys, it is essential to monitor aggregate reports to identify potential issues with email authentication. These reports provide valuable insights into which senders are authenticating correctly and which may be experiencing issues. By analysing these reports, organisations can optimise their email authentication setup and improve deliverability. For instance, if an organisation notices that a particular sender is experiencing issues with DMARC authentication, they can investigate the cause and make necessary adjustments to the sender's setup.
To optimise email authentication, organisations should also consider implementing a feedback loop with their email service providers. This allows them to receive feedback on email authentication issues and make adjustments to their setup accordingly. For example, if an organisation is using a hosted DMARC setup, they can work with their provider to configure a feedback loop that sends alerts when authentication issues are detected.
In terms of specific recommendations, we advise organisations to implement the following best practices:
- Use a centralised DKIM key management system to manage keys across multiple sources
- Implement a colour-coded system to categorise senders based on their trust level and email volume
- Monitor aggregate reports regularly to identify potential issues with email authentication
- Work with email service providers to implement a feedback loop for email authentication issues
- Rotate DKIM keys regularly to maintain security
By following these best practices, organisations can optimise their email authentication setup and improve deliverability, even with multiple sources and senders. This, in turn, can help to protect their brand reputation and prevent email-based attacks.