Postfix/submission/smtpd[xxxxx]: warning: hostname <**> does not resolve to address : Name or service not known

fail2banpostfixsmtpsmtpd

I installed iRedMail on VPS (Ubuntu). Fail2Ban bans my home IP address.

In /var/log/mail.log I see messages like:

postfix/submission/smtpd[32149]: warning: hostname unallocated.sta.lan.ua does not resolve to address 31.43.102.*: Name or service not known

unallocated.sta.lan.ua as I understand is the hostname of my home internet provider.

31.43.102.* is my home IP.

Where is the problem? Is it Internet Provider problem or my fault where my server\iRedMail is not configured properly (if so, how to fix)?

Best Answer

The reverse DNS warning is not really a misconfiguration on your end. Some ISP's just don't provide Forward-confirmed reverse DNS for their addresses.

I'm assuming that this isn't actually causing mail rejection by Postfix but rather a ban by fail2ban. You can check your fail2ban configuration for rules that watch /var/log/mail.log for a pattern that matches the one you posted and then disable that rule. Or you can whitelist your home IP address in the fail2ban configuration by adding it to the ignoreip list in jail.conf.

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