Received header says from localhost instead of hostname

NOYB

When sending an e-mail from my mailcow instance the initial Received header always looks like this:

Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPA id [ID] for <[DEST]>

I expected something with a bit less localhost and a bit more MAILCOW_HOSTNAME. I have seen some anti-spam services flagging this header as being spammy. Is there a way to change (part of) this header to better reflect the actual hostname of the mailcow instance?

NOYB

I wanted to add (there is a limited edit window) that I know that I can change Postfix’ anonymize_headers.pcre, however, that feels unnecessarily dangerous and as something that can easily break other things.

cowboy

I recently installed mailcow, and I am having trouble sending email to hotmail.com, so in trying to troubleshoot the issue, I also noticed my headers show as coming from 127.0.0.1 localhost. Wondering if there’s any way to change this to show my server’s actual IP address and hostname?

iacob28

Hi @cowboy @NOYB

Did you manage to solve this issue?

cowboy

iacob28 Hello. In my case I looked into the issue after I posted and concluded it was better to leave it as is since it helps by not revealing the internal network IP address. Elsewhere in the header, the public IP address is shown along with the hostname.

iacob28

Hi,

If you still need help regarding this issue, the solution is to go to your postfix main.cf file mailcow-dockerized/data/conf/postfix/main.cf and comment this line smtp_header_checks = pcre:/opt/postfix/conf/anonymize_headers.pcre

This regex file replace your Received from header with the localhost IP ( anonymizing your client IP )