@a-luciano It's not entirely safe. Server users get the opportunity to send mail with any email sender. Let's take for example. The user will correct ...

Viewed the logs on the server. There are the following entries: Apr 21 12:25:39 pm mail postfix/submission/smtpd[2253918]: connect from unknown[10.1...

I have the same problem on my server. Some clients do not send mail. In the server and client logs "Sender address rejected: not owned by user". The u...