An operation fails in Plesk: mailmng-outgoing failed: ERROR:__main__:UNIQUE constraint failed: sysusers.id

Symptoms

An operation fails in Plesk with:

Error: mailmng-outgoing failed: ERROR:__main__:UNIQUE constraint failed: sysusers.id

Cause

Inconsistency in the Plesk database.

Resolution

1. Connect to the Plesk server via SSH.

2. Repair the Plesk database:

   # plesk repair db -y

3. Reconfigure mail server:

   # plesk repair mail -y