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We are looking into moving into Exchange Online (but with an Exchange Hybrid server on premises).

What we currently couldn't find out is the backup topic. As there is no way to restore old deleted elements in Exchange Online we would like to use legal hold and prevent that the user can delete anything.

But how big could such a mailbox grow then? Isn´t there a quota restriction which blocks at some point the incoming emails? I think nobody from Microsoft would like to have a 500GB single mailbox on there server because the user isn´t deleting anything in the past 10 years.

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1 Answers1

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In short: the limit of items on Hold is 100 GB and can be increased to unlimited.

In-Place Hold and Litigation Hold uses the Recoverable Items folder to preserve items.

In Exchange Online, the quota for the Recoverable Items folder (in the user's primary mailbox) is automatically increased to 100 GB when you place a mailbox on Litigation Hold or In-Place Hold.

If the Recoverable Items folder reaches or exceeds the 100 GB quota, you can increase the available quota for recoverable items by enabling the user's archive mailbox

Source

If user reached Recovery Items quota, Exchange will not limit user from receiving or sending mail, because Mailbox quota is not reached. Only Recovery Items quota is reached which is separate from Mailbox quota. But it will have other consequences. E.g. user won't be able to delete or modify items, etc.

You can get mailbox Recovery Items size using PowerShell cmdlet Get-MailboxFolderStatistics. I bet there are some third-party products to make mailbox management easier, but I don't have experience with any of it.

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J-M
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