Update: If you need to perform the User > Shared mailbox conversion to preserve access to mailbox of employee that has left the company, we recommend that you follow the Remove a former employee ...
Updated Aug 26, 2026
Version 3.0
Blog Post
@ Mikael.Hagberg, wer83 and Glibglob: Well, this was always possible on-premises quite simply, but not so in O365. Please see
https://technet.microsoft.com/en-us/library/jj710164(v=exchg.150).aspx
@mitchelgw: I beleive you a referring to the fact that we used to require a license for a shared mailbox over 10GB, but that is not the case anymore: Shared Mailboxes now have the same 50GB quota as user mailboxes. Please refer to this, as it might vary on
the version etc. https://technet.microsoft.com/en-us/library/exchange-online-limits.aspx#StorageLimits
https://technet.microsoft.com/en-us/library/exchange-online-limits.aspx#StorageLimits