The default Office 365 maximum message size for messages is 35MB. Because the email text is usually small, this setting essentially restricts the maximum attachment size. You can change the maximum message size for an individual mailbox in the Office 365 admin center or with PowerShell.
To check the current message sending/receiving limt
Get-Mailbox -Identity “UserName@YourDomain.com” | fl maxsendsize,maxreceivesize
To set the message sending/receiving limit to 150 MB
Set-Mailbox -Identity “UserName@YourDomain.com” -MaxReceiveSize 150MB -MaxSendSize 150MB