Reverse DNS does not match HELO
Your PTR record and your HELO/EHLO hostname don't match. Receivers flag this as either misconfiguration or spoofing.
Impact — Medium impact
A mismatch increases your SpamAssassin score and triggers reputation penalties at Gmail and Microsoft. Even if everything else is clean, this one issue can push borderline mail into Junk.
What causes it
- You set PTR when provisioning the server but configured HELO later with a different hostname.
- Your mail server is HELOing with its OS hostname (e.g., 'mail-01.internal') instead of the public hostname.
- The PTR points to a hostname that doesn't exist in forward DNS.
How to fix it
Step 1: Check both values
Current PTR: dig -x . Current HELO: send a test and check Received headers for "EHLO
Step 2: Standardize on one hostname
Pick one canonical hostname (usually mail.yourdomain.com). Make sure: (a) PTR of your IP returns it, (b) A record of the hostname returns your IP, (c) mail server HELOs with it.
Step 3: Verify the chain
The full FCrDNS test: IP → PTR → hostname → A → same IP. If any step breaks, major receivers downgrade you.
Fixed it? Run a fresh test to confirm.
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