On 26/03/2026 14:05, Viktor Dukhovni via Postfix-users wrote:
On Thu, Mar 26, 2026 at 12:16:20PM +0000, 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:
The reason is that that's how the system is configured.
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?
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.
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.
John
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