Thanks to Bill and Benny for the pointer to https://www.postfix.org/DEBUG_README.html#mail. Using tcpdump I figured out that a monitoring task using OpenSsl (with hardcoded mail.example.org) was reusing the same ip (via NAT). You´d call it gremlins đ Joachim
-----UrsprĂźngliche Nachricht----- Von: Bill Cole via Postfix-users <postfix-users@postfix.org> Gesendet: Montag, 12. Februar 2024 16:18 An: Joachim Lindenberg via Postfix-users <postfix-users@postfix.org> Betreff: [pfx] Re: postfix alternating between mail.example.com and real hostname? On 2024-02-12 at 07:07:03 UTC-0500 (Mon, 12 Feb 2024 13:07:03 +0100) Joachim Lindenberg via Postfix-users <postfix-us...@lindenberg.one> is rumored to have said: > I haven´t seen this before, but at present my mail server is kind of > alternating between mail.example.com and the real hostname (or someone > is spoofing my IP-address which I doubt). It is not at all clear what you actually mean by that. Any MTA has a potentially complicated collection of different "identities" used in different context. E.g. in Postfix you've got origin domain names, destination domain names, hostnames used in MX records, and a hostname used in HELO/EHLO greetings. Or is the 'alternating' happening in DNS? We cannot know... > All configuration files I checked indicate the correct setting and > postconf myhostname returns the correct name. Thus I am wondering > whether this might be caused by a recent change of postfix, which > happens tob e 3.5.23 â the mail server is a mailcow-dockerized > instance which still uses images based on debian-bullseye. > > Any idea for the cause and a fix? My guess: Gremlins. You might get more useful answers by including the illuminating information described at https://www.postfix.org/DEBUG_README.html#mail in the section titled "Reporting problems to postfix-users@postfix.org" -- Bill Cole b...@scconsult.com or billc...@apache.org (AKA @grumpybozo and many *@billmail.scconsult.com addresses) Not Currently Available For Hire _______________________________________________ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org _______________________________________________ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org