Reverse DNS (FCrDNS) Checker
Check forward-confirmed reverse DNS (FCrDNS) for a mail IP or domain.
Enter a sending IP address or a domain to check its reverse DNS (PTR) and confirm it is forward-confirmed (FCrDNS). Many mailbox providers expect a sending IP's PTR name to resolve forward back to the same IP. When it does not, your mail is more likely to be throttled, junked or refused. We run the lookups live over an encrypted connection. Nothing is stored.
Give an IPv4 address to check it directly, or a domain to check the IPs it sends from.
This tool checks forward-confirmed reverse DNS (FCrDNS) for a mail IP or hostname. FCrDNS is a two-step test that mail servers run on every connection. First, it takes the connecting IP and looks up its PTR record to get a hostname. Second, it resolves that hostname forward through its A (or AAAA) record and checks that it points back to the original IP. If both directions agree, the IP passes FCrDNS; if the PTR is missing, or the forward record does not return the same address, it fails.
Why FCrDNS is a deliverability gatekeeper
FCrDNS proves that the same party controls both the IP's reverse DNS and the matching forward record, which is hard for a casual spammer to fake. Receiving servers use it as a low-cost reputation signal: a fail commonly leads to greylisting, spam-folder placement or an outright rejection, regardless of how good your SPF, DKIM and DMARC are. It is one of the oldest and most universally applied anti-abuse checks in SMTP.
How to read and fix the result
A pass means the PTR hostname and its forward record both resolve to the tested IP. A fail usually has one of three causes: no PTR record at all, a PTR pointing to a hostname whose A record returns a different IP, or a forward record that simply does not exist. To fix it, ask the owner of the IP block (your provider) to set the PTR to a hostname you control, then publish a forward A record for that exact hostname pointing back to the same IP. Use the PTR Record Checker to inspect the reverse half on its own. Getting this right is part of a complete sending setup; see how to enforce for the wider picture.
Frequently asked questions
What does forward-confirmed reverse DNS mean?
It means the reverse lookup and the forward lookup agree. The IP's PTR record gives a hostname, and that hostname's A or AAAA record resolves back to the same IP. When both directions match, FCrDNS passes.
Why is my IP failing FCrDNS?
The usual reasons are a missing PTR record, a PTR pointing to a hostname whose forward record resolves to a different IP, or a hostname that has no A record at all. Both halves of the lookup must reference the same address.
How do I fix an FCrDNS failure?
Ask the operator of the IP block to set the PTR to a hostname you control, then create a matching forward A (or AAAA) record for that exact hostname pointing back to the same IP. Allow DNS to propagate, then re-test.
Does the PTR hostname have to match my email domain?
It does not have to be your exact From domain, but it should be a meaningful hostname you control and ideally be related to your sending infrastructure. What matters most for FCrDNS is that the forward record resolves back to the same IP.
Will passing FCrDNS guarantee inbox placement?
No. FCrDNS is a baseline trust check, not a full reputation system. You still need aligned SPF and DKIM, a published DMARC policy and good sending behaviour, but failing FCrDNS will undermine all of those.
Can I set FCrDNS myself if I am on shared hosting?
Only partially. You can usually create the forward A record yourself, but the PTR side is controlled by the IP owner. On shared platforms you may share an IP whose PTR you cannot change, in which case you must rely on the provider's own reverse DNS.