Question Roundcube or Outlook - INTERNAL ERROR - Could not load message from server.

[Neotop]

Hello community,

i have the problem that when a very specific customer sends me an email, I can't open it in Outlook and Roundcube. The Android phone vibrates several times and shows the message repeatedly on the display.

Somehow the server cannot process the message.
This does not happen with all other mails from other customers and runs normally.

However, I can read them from time to time.

Unfortunately, I'm at the end of my knowledge, I don't know what to do anymore. Maybe you still have ideas.

 

[Monty]

Anything relevant in /var/log/maillog and /var/log/plesk-roundcube/errors ?

 

[StefSabi]

IMAP Error: Login failed for xxx@xxx.com against localhost from xx.xxx.xxx.xxx.. AUTHENTICATE PLAIN: Authentication failed. in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_imap.php on line 211 (POST /?_task=login&_action=login)