Question
Postfix/smtpd hostname does not resolve to ip (but it does!)
Hello;
I’ve been searching and reading through numerous posts, but can’t seem to find a resolution to my email issue.
I’m seeing the following in my logs, every few minutes;
Apr 10 23:53:50 toronto01 postfix/smtpd[2497]: warning: hostname toronto01.kasnetwork.com does not resolve to address 159.203.56.205
Apr 10 23:53:50 toronto01 postfix/smtpd[2497]: connect from unknown[159.203.56.205]
Apr 10 23:53:50 toronto01 postfix/smtpd[2497]: disconnect from unknown[159.203.56.205]
I have reverse pointers setup and the hostname does resolve at mxtoolbox –> https://mxtoolbox.com/SuperTool.aspx?action=ptr%3a159.203.56.205&run=toolpage
I just can’t seem to figure out why this error occurs as the logs offer no real explanation. No rejected messages, or SASL login failed, etc., such as this entry;
Apr 10 23:59:42 toronto01 postfix/smtpd[2666]: warning: hostname 80-69-247-10.pasargadnet.ir does not resolve to address 80.69.247.10
Apr 10 23:59:42 toronto01 postfix/smtpd[2666]: connect from unknown[80.69.247.10]
Apr 10 23:59:45 toronto01 postfix/smtpd[2666]: warning: unknown[80.69.247.10]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Apr 10 23:59:45 toronto01 postfix/smtpd[2666]: disconnect from unknown[80.69.247.10]
I don’t know where this “connection” is coming from. It appears as if the server is connecting to itself, but for what reason and why it doesn’t resolve I just can’t understand.
Any pointers would be greatly appreciated!
Thanks;
Kyle
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As a follow up this morning, here is an excerpt from my mail.log;
You can see how often I’m seeing this warning, but what also interests me is if I do a reverse lookup on any of these (including my ip), they ALL resolve to the hostname shown.
91.200.12.173 does indeed resolve to dedic878.hidehost.net (https://mxtoolbox.com/SuperTool.aspx?action=ptr%3a91.200.12.145&run=toolpage#) as do the rest.
Is this something I have incorrectly set in a config file?
Thanks;
Kyle