Forward the email processing logs to SIEM solutions
the solution should have the ability to integrate with SIEM solutions by forwarding the email processing logs and events by any means
Rahul Verma commented
For SIEM Solutions, I suggest you a best security product that is LTS Secure. LTS Secure SIEM is capable of offering an effective and efficient means to monitor your network round the clock. Continuous monitoring from SIEM includes all devices, servers, applications, users and infrastructure components.
GFI MailEssentials logs all events to the Windows Event log.
Any SIEM software can monitor the windows event log making important possible.
Email logs would be a drastic approach due to the amount of data involved, however any email failure for example would be logged in the windows event log making alerting of any issues possible.