When trying to synchronize Subscription with its Service plan following error appears:
PLESK_ERROR: Bounce mode not supported <example.com> Bounce with message Reject
When conflicting rules are set in Service plan and Mail client settings subscriptions cannot be synchronized.
Bounce mode not supported means that mail to non-existing user function is enabled in Service plan and disabled on the Mail server.
To synchronize subscription with service plan set Reject in Service plans > example > Mail > Policy on mail for non-existent users.
Alternatively for MailEnable, enable Generate NDRs in MailEnable > Postoffice > Properties > General > General Settings > Generate NDRs.