- Plesk 12.5 for Windows
Outgoing Mail Control is not blocking mails which exceed defined limit.Outgoing Mail Control Statistic for subscription is not counting sent mails.
Messages sent via the MailEnable webmail are not counted against the corresponding subscription's outgoing mail limit, because they are placed directly into the mail queue bypassing Plesk. Plesk refer to documentation
This is Plesk internal issue with ID #PPPM-4152 which is planned to be fixed in future Plesk updates.
Use Horde webmail. It can be installed using Plesk autoinstaller and chosen at Subscriptions > example.com > Mail > Mail Settings > Webmail .