Office 365 Showing Mailbox Full When it is Not
I had a user reporting that Outlook was giving them an error saying "Mailbox Full" even though they only had 30GB of mail. I checked the Exchange admin center and it said that the user had a 100GB limit and was only using 30GB.
I connected to EOL powershell and set the size limit on the mailbox manually using the command below.
Get-Mailbox User1 | Set-Mailbox -ProhibitSendReceiveQuota 100GB -ProhibitSendQuota 99GB
Oddly enough the command returned: "WARNING: The command completed successfully but no settings of 'User' have been modified.". However, after a minute the Outlook error went away and the mailbox started working again.
From what I can gather it looks like mailbox size limits transfer over when you migrate a mailbox using Hybrid. If you are migrating multiple mailboxes it might be a good idea to run the command below to send the max limit for all mailboxes:
get-mailbox | Set-Mailbox -ProhibitSendReceiveQuota 100GB -ProhibitSendQuota 99GB