Issue Email is not working Invalid mail address '@**

[mehdi-ra]

Server operating system version

Debian 11.7 x86_64

Plesk version and microupdate number

18.0.53.2

Hello, dear gentelmen.
The problem suddenly starts and we don't know the cause!. One day we woke up and the email service was not working anymore. I don't know if someone messed up the email configuration, but anyway, I can't send any emails, and as you can see in the log files, I'm getting strange error logs.
can anyone help me to understand what is the problem? Or help me to solve the problem? This is affecting our business so I decided to reach out for help here.

Product version: Plesk Obsidian 18.0.53.2
OS version: Debian 11.7 x86_64
Build date: 2023/06/19 12:00
Revision: 3bb4bcb8a6856cd7947168ad037a180dc06fbcf4

# Aache version
Server version: Apache/2.4.56 (Debian)
Server built: 2023-03-08T03:05:04

mail.err file.
[Edited by admin, unlinked the mail.err file as it contains sensitive information.]

 

[Peter Debik]

In your mail.err file you have many entries like
Jul 24 23:59:07 server plesk_saslauthd[350806]: Invalid mail address '@<domain>'
This means that for authentication the login name is incomplete. It needs to be the full mailbox name, not just the @<domain> part. Please check your email client(s) that they use proper authentication with the full mailbox name.