Error:
This message wasn't delivered to anyone because it's too large. The limit is 10 MB. This message is
This message won't be sent because it's too large
#550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization ##
Solution:
Adjust the limits with the following powershell commands:
Set-TransportConfig -InternalDsnMaxMessageAttachSize #MB
Set-TransportConfig -ExternalDsnMaxMessageAttachSize #MB
then
Set-TransportConfig -MaxReceiveSize #MB -MaxSendSize #MB
or
Set-Mailbox "User" -MaxSendSize #MB -MaxReceiveSize #MB