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

>>On Thu, Mar 26, 2026 at 12:16:20PM +0000, Sad Clouds via Postfix-users wrote:
>>>1. When sending from [email protected] to [email protected] and this
>>>domain is in virtual_mailbox_domains, then MUA submission on port 25 is
>>>permitted. Is this normal and is there a way to disable submission
>>>completely for port 25 and only use this port for mail relay?

>On 26/03/2026 14:05, Viktor Dukhovni via Postfix-users wrote:
>>Accepting mail for your own domains on port 25 is not submission, the
>>SMTP server cannot reasonably distinguish between an MTA sending inbound
>>mail and an MUA doing the same thing.

On 26.03.26 15:44, John Fawcett via Postfix-users wrote:
>In general no, but the distinction could be made based on a sender 
>present in smtpd_sender_login_maps. It would need a new configuration 
>parameter to be able to reject mail from an unauthenticated sender 
>where authentication is not enabled.

smtpd_sender_login_maps is only usable when SASL is enabled, which is not 
true on OP's port 25.

As i wrote in my previous e-mail, the solution might be disabling client 
machines from accessing port 25, in directions to mail server and the 
internet.

End-stations are usually NOT supposed to connect to port 25 anyway.

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