Office 365 now supports larger email messages—up to 150 MB
Posted by Support Team on 08 February 2016 10:34 PM

The default maximum message size for Office 365 mailboxes is 25 MB, and they aren’t going to change the setting on existing accounts. It turns out that some clients want an even smaller setting than 25 MB and many don’t want to change the current setting at all. So instead of Microsoft foisting a one-size-fits-all setting onto everyone, they are now giving Office 365 customers the freedom to choose the maximum size setting that’s right for them.

Customizable maximum message size

You can customize the maximum allowed message size for any and all your mailboxes however you see fit. Want to go wild and allow everyone to send and receive 100 MB size messages? Go for it. Want to restrict students in your school from sending messages larger than 5 MB, while the faculty can send up to 50 MB? No problem. Do you have a hybrid mail configuration (some mailboxes on-premises, some in the cloud) and you want a consistent 10 MB restriction regardless where the mailbox is hosted? We have you covered. Whatever custom configuration you want to apply, whether for one, some, or all your mailboxes you can do it—as long as it’s between 1 MB and 150 MB.

You customize the message size in the Exchange Admin Center, which requires global administrator role privileges.

You can change the default for your organization by adjusting the default message size restriction. Simply select recipients mailboxes then click “. . .” and select Set default message size restrictions.

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You can then specify the maximum message size for new mailboxes (those you create in the future).

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To edit multiple mailboxes select recipients > mailboxes and select multiple mailboxes. Then from the Bulk Edit pane under Message Size Restrictions select Update.

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Finally, you can customize a single mailbox by selecting recipients > mailboxes and then select a user’s mailbox. Click the edit icon , then under Message Size Restrictions, click View details and then specify the maximum message size.

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Use the Exchange Admin Center or Remote PowerShell

If your organization is comprised of less than 1,000 mailboxes, you’ll likely end up using the Exchange Admin Center user interface to make changes. But if your organization has more than 1,000 users, you may want to make these changes via Remote PowerShell. Updating thousands of mailboxes at a time can take a while to complete—a rough rule of thumb is around 5 to 10 minutes per 1,000. And while replicating the updates across the service typically takes an additional 15 minutes, allow up to 30 minutes after the update process is finished before testing out the new settings.

Examples of the common commands you might use to customize these settings via Remote PowerShell include:

Update a single mailbox Set-Mailbox -Identity -MaxSendSize 75MB -MaxReceiveSize 75MB
multiple mailboxes 
(“alias”, “alias2”, “alias3”) | % {Set-Mailbox –Identity $_ -MaxSendSize 75MB -MaxReceiveSize 75MB}
Update all mailboxes  Get-Mailbox | Set-Mailbox -MaxSendSize 75MB -MaxReceiveSize 75MB
Update the default settings
(For mailboxes you create in the future.)
Get-MailboxPlan | Set-MailboxPlan -MaxSendSize 75MB -MaxReceiveSize 75MB


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