What happens as the Outlook mailbox fills up and eventually reaches the Office 365 50GB quota:

• Users will receive a warning when their mailbox quota has reached 24.5GB.
• At 49.5GB, users will no longer be able to send messages, though emails will continue to be received until the mailbox is 50GB.
• At 50GB, users will no longer be able to send or receive emails. Users will not be able to send emails again until their mailbox is reduced in size to below the 49.5GB.