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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