5 feb 2018

Office 365: Customize the maximum message size to 150MB

The default maximum message size for Office 365 mailboxes is still 25 MB but you can choose the size setting that’s right with a maximum size of 150MB

#Product Affected
Office 365, Exchange Online

For your convenience use PowerShell to do it

Update a single mailbox
Set-Mailbox -Identity alias@domain.com -MaxSendSize 150MB -MaxReceiveSize 150MB

Update multiple mailboxes 
(“alias”, “alias2”, “alias3”) | % {Set-Mailbox –Identity $_ -MaxSendSize 150MB -MaxReceiveSize 150MB}

Update all mailboxes
Get-Mailbox | Set-Mailbox -MaxSendSize 150MB -MaxReceiveSize 150MB

Update the default settings (For mailboxes you create in the future.)
Get-MailboxPlan | Set-MailboxPlan -MaxSendSize 150MB -MaxReceiveSize 150MB