Running mail reliably.
WHAT TO MONITOR
Queue size and age Deferred mail Rejection rates Authentication failures Storage use Blocklist status Certificate expiry
WHAT A GROWING QUEUE INDICATES
A delivery problem, or an outbound flood.
WHAT TO CHECK IN LOGS
Why messages were rejected or deferred, which is usually stated precisely.
WHAT TO BACK UP
Mail storage Configuration Account data
WHAT TO TEST
Restoring a mailbox.
WHAT TO PLAN FOR
Storage growth, which is relentless.
WHAT TO CONFIGURE
Retention policy, where appropriate and lawful.
WHAT TO DOCUMENT
The configuration, and why it is as it is.
WHAT TO AUTOMATE
Certificate renewal Backups Account provisioning
WHAT TO REVIEW PERIODICALLY
Accounts that are unused Forwarding rules nobody created Aliases pointing nowhere
WHY THAT SECOND POINT
Forwarding rules the user did not create are the classic sign of a compromised mailbox.
WHAT TO KEEP
Logs, for long enough to investigate.
