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Office 365 Shared Mailbox Size Limits

Sep 9, 2013 by Emma Robinson

Until recently (Sept 2013), the maximum size limit for Office 365 Shared Mailboxes was 5GB but Microsoft has now increased this limit to 10GB.

New Office 365 Mailbox Size Limits

New Office 365 Mailbox Size Limits

Many Office 365 users, including ourselves, have set mailbox size limits on our Shared Mailboxes to make sure they stay under the old 5GB limit.

PS C:\Users\burns_000\Desktop> get-mailbox -ResultSize Unlimited -filter {RecipientTypeDetails -eq "SharedMailbox" -or RecipientTypeDetails -eq "RoomMailbox"} | Select DisplayName, Prohibit*Quota | ft
DisplayName ProhibitSendQuota ProhibitSendReceiveQuota
----------- ----------------- ------------------------
Test Shared Mailbox 4.75 GB (5,100,273,664 bytes) 5 GB (5,368,709,120 bytes)
Test Conference Room 4.75 GB (5,100,273,664 bytes) 5 GB (5,368,709,120 bytes)
Office 365 Support Mailbox 4.75 GB (5,100,273,664 bytes) 5 GB (5,368,709,120 bytes)
PS C:\Users\burns_000\Desktop>

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So what’s the fastest way to increase the quota on all of our shared and resource mailboxes to take advantage of this new limit? PowerShell of course!

Setting quotas on Shared Mailboxes

Firstly, connect to Office 365 using PowerShell and then run the following cmdlet.

get-mailbox -ResultSize Unlimited -filter {RecipientTypeDetails -eq "SharedMailbox" -or RecipientTypeDetails -eq "RoomMailbox"} | Set-Mailbox -ProhibitSendReceiveQuota 10GB -ProhibitSendQuota 9.75GB -IssueWarningQuota 9.5GB

Find the size of all Shared Mailboxes

We have also provided a script that will connect to Office 365 and export the mailbox sizes (and size limits) of all the shared mailboxes to a CSV file. You can find this script over at the Microsoft Script Repository.

Our Office 365 reporting software also includes a report dedicated to Office 365 Shared Mailbox Sizes.