When you provision new Office 365 tenant, by default maximum send / receive message size is 35 MB. At the first look that is not a big issue, but if you have plan to migrate mails to Office 365, all mails larger than 35 MB will fail.

Luckily, one easy PowerShell command can solve that problem, and you will be able to increase message maximum size to 150 MB. That can be done with configuring Mailbox Plan or configuring single mailbox.

* Changing Mailbox Plan will NOT affect existing mailboxes. Only new mailboxes will apply parameters from Mailbox Plan.

With following commands you can check status of maximum message size at Mailbox Plan level or single mailbox.

Get-MailboxPlan | fl Name, MaxSendSize, MaxReceiveSize

Name           : ExchangeOnlineEnterprise-48f1445a-9d98-43ef-863f-20b799d79850
MaxSendSize    : 35 MB (36,700,160 bytes)
MaxReceiveSize : 36 MB (37,748,736 bytes)

Get-Mailbox Vladimir | fl Name, MaxSendSize, MaxReceiveSize

Name           : Vladimir
MaxSendSize    : 35 MB (36,700,160 bytes)
MaxReceiveSize : 36 MB (37,748,736 bytes)


If you want to change Mailbox Plan or single mailbox, following commands will do that.

Set-MailboxPlan -Identity PlanName -MaxSendSize 150MB -MaxReceiveSize 150MB

Set-Mailbox -Identity MailboxName -MaxReceiveSize 150MB -MaxSendSize 150MB


After this, your Mailbox Plan / single mailbox will be configured to support message up to 150 MB.



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