1. Objective
In this article will show you how to remove a mailbox from quarantine in Exchange Server 2013.
2. Problem Description
A mailbox could becomes quarantine when it detects clients that are taking up too much of the Store’s attention because something is going wrong. MAPI clients like Outlook use multiple threads within the Store process when they connect to mailboxes. If one or more of these threads “freeze” for some reason, they can cause the Store to consume more CPU than it should in an attempt to service the thread. The problem might be caused by corrupt mailbox data or a software bug in either the client or Store process or some other reason such as network failure. In any case, it’s a bad thing if threads freeze or terminate abnormally.
The effected mailbox will not be able to send or receive any mail and will got the following error when accessing to OWA. 
Likewise, when other users try to send an email to the effected mailbox, they will get the follow error reply.
3. Problem Resolution
First of all, we need to list the email that have become quarantine by executing the following command.
Get-Mailbox –Server <Server-Name> –ResultSize unlimited | Get-MailboxStatistics | Where-Object { $_.IsQuarantined –eq $True } | Select DisplayName,IsQuarantined,QuarantineEnd
Then, get the mailbox name of the quarantine email execute the following command.
Get-Mailbox
For this time, we can release the quarantine mailbox with following command.
Disable-MailboxQuarantine <mailbox>
To verify that the affected mailbox had been removed from the quarantine, execute the following command again.
Get-Mailbox –Server <Server-Name> –ResultSize unlimited | Get-MailboxStatistics | Where-Object { $_.IsQuarantined –eq $True } | Select DisplayName,IsQuarantined,QuarantineEnd
Now there should be mo more any mail in the quarantine list.
