[pfx] Re: Disabling MUA submission for smtpd on port 25

On Thu, 26 Mar 2026 14:08:27 +0000
Allen Coates via Postfix-users <[email protected]> wrote:

> On 26/03/2026 12:16, Sad Clouds via Postfix-users wrote:
> > It looks like there is no AUTH, but for some reason I can still submit
> > mail on port 25 in some cases. There are two cases I'm testing:
> 
> Some while ago, I had a spate of spam messages, addressed to me, and claiming to be from "support" or "accounts" or
> "personnel" (at) "mydomain".   They were coming in - unauthenticated - on port 25.
> 
> These were caught by placing an entry in the sender_access file, resolving to anything from "mydomain", with an action
> of "permit_sasl_authenticated, reject"

Thanks for the tip, this seems to be a good way to block users in
my virtual domains from sending mail via port 25

# cat /etc/postfix/smtpd_sender_access
example.com  REJECT

Now if anyone from @example.com is sending unauthenticated mail to port
25, it gets rejected.

I have a separate /etc/postfix/mua_sender_access for the authenticated
submission smtpd process.
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