Unable to login into Roundcube webmail on Plesk server: Login Failed

Symptoms

• Unable to login into mail account with error:

  Login Failed

• The following error shows up in /var/log/plesk-roundcube/error.log:

  IMAP Error: Login failed for jdoe@example.com against localhost from 203.0.113.2. AUTHENTICATE PLAIN: Authentication failed. in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_imap.php on line 211 (POST /roundcube/?_task=login&_action=login)

Cause

Password is incorrect.

Resolution

Change mail account password:

1. Log into Plesk
2. Go to Domains > example.com > Mail > Mail Accounts > jdoe@example.com
3. Change the password:
   
4. Click Ok