Service health

Monitor SMTP transport, mailbox services, spam filtering and supporting runtime services independently.

Operational indicators

• SMTP service availability.
• Authenticated submission availability.
• IMAP availability.
• Queue size and deferred messages.
• Mailbox-storage utilisation.
• Spam-filter health.
• Authentication failures.

Log correlation

When investigating a mail problem, correlate events by recipient, sender, message ID, queue ID and time rather than relying on a single log line.

Maintenance

Validate configuration before restarting services. Repeated restarts may hide the underlying reason for a recurring failure.