I'm trying to move an on-premises Exchange mailbox to Microsoft 365 using a Business Standard license. The mailbox is larger than 50 GB but under 100 GB, and the additional 50 GB Exchange Online storage option doesn't seem to apply until the mailbox already exists in Exchange Online.
I've confirmed that Exchange_Storage_50GB is provisioned, rerun the license assignment, checked for on-premises mailbox limits, and verified that existing cloud mailboxes receive the additional capacity. I also removed and re-added the storage option, then waited both 15 minutes and a full day, but the migration target still appears capped at 50 GB.
Would temporarily assigning an Exchange Online Plan 2 or an E3-equivalent license allow the remote move to complete? Is there another way to make the 100 GB target quota apply before migration?
3 Answers
Try assigning Exchange Online Plan 2 temporarily rather than jumping straight to E3. Plan 2 includes the larger mailbox quota and is usually a much cheaper way to test whether the license type is the blocker. The additional-storage option may not be evaluated for a mailbox that hasn’t been created in Exchange Online yet.
Just to confirm, is the mailbox you’re moving larger than 50 GB but still below 100 GB? That would explain why the migration is hitting the base Business Standard limit instead of recognizing the extra storage.
Yes, that’s exactly the situation. The mailbox is over 50 GB but under 100 GB.
Check the move report and the target mailbox quota directly. Seeing the storage add-on as provisioned doesn’t necessarily mean the migration target has received a 100 GB effective quota. A temporary Plan 2 or E3 assignment is reasonable, but verify the quota again after switching back to Business Standard plus the add-on. If it falls back to 50 GB, the mailbox may stop sending or receiving once it exceeds that limit.
E3 mainly helps here because it includes Exchange Online Plan 2. A standalone Plan 2 license should provide the same migration quota at a lower cost.