Checklist
Microsoft 365 Mailbox Bloat Checklist.
Before changing policies or asking users to delete mail, gather the evidence.
A useful review connects tenant-level storage signals with mailbox-level evidence, policy context and destination readiness. Work through these six areas to create a clearer basis for administrator-controlled next steps.
1. Identify the largest mailboxes
Start with the most visible pressure points, then compare size with growth patterns to identify the fastest-growing risks.
2. Check archive usage
Archive growth can hide the true scale of storage pressure, especially when retention policies have been left untouched for years.
3. Look for attachment-heavy patterns
Large files sent to multiple recipients can multiply storage usage across mailboxes and archives.
4. Review retention and deletion assumptions
Ground retention changes in a clear understanding of compliance, user needs and recoverable item behaviour.
5. Check destination readiness
If SharePoint is being considered as a destination for offloaded data, check storage headroom, site structure, permissions, and ownership first.
6. Produce a decision report
Turn the evidence into a clear decision: retain, clean up, archive, review licensing, plan future optimisation or investigate further.
Mailbox health snapshot
Get a free mailbox health snapshot.
A practical first view of mailbox health, storage pressure and priority risks — designed for safe, evidence-backed Microsoft 365 decision-making.