ErrorQuotaExceeded During Mail Migration
Increase the Office 365 mailbox storage quota to complete migration.
Error Message
Mail Migration Error
Fatal error during migration process: ResponseCodeType.ErrorQuotaExceeded
This error terminates the migration when the target mailbox reaches capacity.
Mailbox Storage Full
Root Cause
Insufficient Target Mailbox Storage
The destination Office 365 mailbox lacks sufficient storage capacity to accommodate the migrated email data. The target mailbox has reached its storage quota limit during the migration process.
Default Office 365 Mailbox Sizes
- • Exchange Online Plan 1: 50 GB
- • Exchange Online Plan 2: 100 GB
- • Microsoft 365 Business: 50 GB
- • Enterprise E3/E5: 100 GB
Solution
Increase Mailbox Storage Quota
Check Current Usage
In Exchange Admin Center, check the current mailbox size and compare it to the source Gmail mailbox size.
Increase Quota (if possible)
Go to Exchange Admin Center → Recipients → Mailboxes → Select user → Mailbox features → Storage quotas. Increase limits if your license allows.
Upgrade License (if needed)
If the user needs more than the license allows, upgrade to a higher license tier (e.g., E3/E5 for 100GB mailboxes).
Restart Migration
After increasing the quota, restart the migration. Delta pass will continue from where it stopped.
Archive Mailbox Option
Alternative Approaches
- • Use date filters to migrate only recent emails first
- • Enable In-Place Archive for unlimited archive storage
- • Clean up the source mailbox before migration
- • Delete unnecessary emails from the target after partial migration