Unable to log in to webmail on a Plesk for Windows server: Unknown or Disabled User!

Symptoms

• When accessing mailbox existing in Plesk via the MailEnable webmail interface, the following error is provided:

  Unknown or Disabled User!

• Plesk may be recently upgraded from Onyx to Obsidian.

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• plesk repair mail command may be recently executed on the server.

Cause

The password for the mailbox was previously changed from outside Plesk:

• using the MailEnable webmail interface;
• via MailEnable Admin console.

Plesk forcibly replaces all passwords with the ones stored in the psa database during the upgrade/execution of plesk repair mail command. Thus, changes applied from outside are rewritten.

Resolution

Update password via Plesk UI:

1. Log into Plesk.
2. Navigate to the affected mailbox in Domains > example.com > Mail tab > Mail Accounts > [email protected].
3. Provide the required password in the Password and Confirm password fields:
   
4. Apply changes.