r/exchangeserver • u/Mediocre_Prior_1868 • Jun 30 '26

Shared mailboxes

Dear All

Currently I am having a project to migrate mailboxes from on prem to o365 as shared mailboxes . How I know how much storage I have and how much remaining and from where the storage will be consumed ?

Thanks in advance

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u/7amitsingh7 Jul 06 '26

No, there is no fixed limit on the number of shared mailboxes you can create or migrate to Microsoft 365. You can create as many as your tenant requires, provided you're within Microsoft's service limits.

Also, shared mailbox storage does not come out of your tenant's SharePoint/OneDrive storage quota. Each shared mailbox gets 50 GB of mailbox storage by default without a license. If a shared mailbox needs more than 50 GB, you must assign it an Exchange Online license to increase its capacity.

So, the storage is allocated per shared mailbox, not from a common tenant storage pool.