For a Microsoft 365 Business Basic user with a 50 GB primary mailbox and a Purview retention policy applied, does content moved into Recoverable Items count against the same 50 GB mailbox limit? For example, when a user deletes an email and retention keeps it in Recoverable Items, is that retained content using the primary mailbox storage or a separate quota?
3 Answers
They are separate storage areas, but retention behavior matters. Content in Recoverable Items is subject to that area's quota while it remains there. After the retention period expires, it may be permanently removed from the mailbox, although Purview retention can preserve it in the compliance store according to the policy. That is different from a litigation hold, which can preserve mailbox content indefinitely and usually comes with larger Recoverable Items limits.
Recoverable Items has its own quota, separate from the primary mailbox. The limit is commonly around 30 GB for mailboxes without a hold and can be higher when a mailbox is on hold. So a mailbox might have plenty of free space in the primary mailbox while Recoverable Items is nearly full. If that separate quota is exhausted, users may be unable to delete more messages, and Outlook can start showing mailbox-full errors.
You can check how much space the deleted and retained content is using with Exchange Online PowerShell, for example: Get-MailboxStatistics -Identity [email protected] | Select TotalDeletedItemSize. That reports the Recoverable Items usage so you can compare it with the applicable quota.
Classic Outlook can also become pretty noisy in that situation, repeatedly reporting that the mailbox is full even when the primary mailbox itself doesn't look close to its limit.