Mail logs are not rotated during Plesk Daily Maintenance

Symptoms

The mail logs (in /var/log/maillog) are not moved to the processed file (/var/log/maillog.processed) during Plesk Daily Maintenance.

Cause

None of the domains in the server has the mail service enabled. This can be confirmed with the following command (it should have no output):

# plesk db "SELECT * FROM DomainServices WHERE type='mail'"

Resolution

Plesk only rotates mail logs when at least one domain has the mail service enabled. To fix this, enable mail for any one domain as instructed here: How to activate the mail service for a domain