Reverse DNS (rDNS) is a DNS record that maps an IP address back to a domain name — the opposite of a normal DNS record, which maps a domain name to an IP address. This article is for anyone whose incoming email to Titan Mail is being rejected because the sending server's rDNS is missing or doesn't match. After reading it, you'll understand why this happens and know what to ask your mail provider to fix.
Troubleshooting
Problem: An email sent to your Titan Mail address is rejected. The sender sees a bounce-back message similar to this:
450 4.7.25 Client host rejected: cannot find your hostname, [xxx.xxx.xx.xx]
Cause: Titan checks the rDNS record of the sending server's IP address to help block spam. This bounce happens when that IP address has no rDNS record, or when its rDNS record does not match its forward DNS record. For example, "abc.com" pointing to IP address "1.2.3.4" does not by itself mean that IP address "1.2.3.4" points back to "abc.com" — forward DNS and rDNS are two separate records, and both need to be set up correctly.
Fix:
- Identify the mail server that sent the rejected email. This is usually the sender's own mail provider, not Titan.
- Contact that mail provider and ask them to set up a PTR record (the DNS record that provides rDNS) for the sending server's IP address, so it matches the server's forward DNS. Only the provider that manages the sending server can set this up.
What success looks like
The sending server's rDNS record matches its forward DNS record, and email from that server reaches your Titan Mail inbox without being rejected.