Does my hostname need to match my rDNS lookup? (Forward-confirmed reverse DNS - FCrDNS)

Yes, your hostname and your reverse DNS lookup need to match each other. That bidirectional match is called FCrDNS (Forward-confirmed reverse DNS), and many receiving mail servers check for it before they trust your email.

Here's how the loop works. Your sending IP has a PTR record that points to a hostname (the reverse lookup). That hostname then has an A record that points back to the original IP (the forward lookup). FCrDNS passes only when both directions resolve to the same value. If they don't match, the loop breaks.

A passing example looks like this:

• IP 192.0.2.1 has PTR pointing to mail.tidalmail.com
• mail.tidalmail.com has an A record pointing back to 192.0.2.1
• Both directions agree. FCrDNS passes.

Still a failing example looks like this:

• IP 192.0.2.1 has PTR pointing to mail.tidalmail.com
• mail.tidalmail.com A record resolves to 203.0.113.55 (a different IP)
• The loop doesn't close. FCrDNS fails.

Why does this matter? FCrDNS proves that your DNS configuration is intentional and consistent on both sides. Anyone can set a PTR record to claim any hostname. But if the A record on that hostname doesn't point back to your IP, the claim falls apart. That asymmetry is a classic sign of misconfigured infrastructure, or someone trying to impersonate a legitimate server.

What actually happens when FCrDNS fails depends on the receiving server. Some will defer your email with a temporary error and retry. Some will reject it outright. Others will accept it but quietly reduce your trust score, which shows up later as lower deliverability or inbox placement. Bulk senders in particular are expected to have FCrDNS set up correctly. Missing it is a red flag that ISPs factor into trust scoring.

To verify your own setup, you can use the dig command (on Mac or Linux) or nslookup (on Windows). First look up the PTR for your sending IP, then forward-resolve the hostname that comes back. If both steps return the same IP, you're good.

If there's a mismatch, the fix usually lives on two sides. The PTR record is controlled by whoever owns the IP (often your hosting provider or ESP, not you directly). The A record is in your DNS zone. Both need to be updated in sync. If you're on a shared IP through an ESP, they manage the PTR and you don't need to worry about it. But if you're sending from a dedicated IP, this is your responsibility to set up correctly.

Not sure if your setup passes? Our free Email Header Analyzer can show you what a received message actually looks like on the other end, which makes it easy to spot FCrDNS issues hiding in delivery headers. Or drop us a message on the SOS hotline if something's broken and you can't figure out which side needs fixing.