Increasing attachment limits in Office 365/Exchange Online

The default limit for messages in Microsofts online mailboxes is 35MB. You can change this limit from powershell commands.

If you don’t know how to get started with Powershell admin then look at my previous posting: Send As From a different email domain in Office 365 Exchange Online.

There are 2 limit parameters: MaxReceiveSize and MaxSendSize.

The command for changing the mailbox limit parameters is:

Set-Mailbox John.Doe -MaxReceiveSize 55MB -MaxSendSize 55MB

Substitute John.Doe for the mailbox you want to change.

To change all mailboxes use this:

Get-Mailbox -Resultsize Unlimited | Set-Mailbox -MaxReceiveSize 55MB -MaxSendSize 55MB

And to set the limits for all new mailboxes use this:

Firstly find out which mailbox plan is the default:

Get-MailboxPlan | fl name,maxsendsize,maxreceivesize,isdefault

You will see a list of mailbox plans (name followed by a GUID) only one of which is marked as the default and they will also show the current limits.

To change the default mailbox plan use this command:

Set-MailboxPlan <em>ExchangeMailboxPlan-GUID</em> -MaxSendSize 55MB -MaxReceiveSize 55MB

Replace ExchangeMailboxPlan-GUID with the default plan listed previously.

Always remember to close your session with:

Remove-PSSession $Session

Author: James

IT Manager - Network, Web coding, MS SQL and Online Mapping expert

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