Organisational level: and/or Receive connector level ...Best to do both.


Organisational Level


The message size limits on the organization level can be set through the Exchange Management Console via Organization Configuration > Hub Transport > Global Settings by opening the Properties of Transport Settings:



  Of course, you can also view the settings using the Exchange Management Shell using Get-TransportConfig

 

 


 As you can see, the default value in Exchange 2010 is 10240 (10 MB) for both receive as well as send message sizes. If you require a higher value, for example to enable people to send and receive larger attachments, you can use the EMC or Set-TransportConfig:


Set-TransportConfig –MaxReceiveSize 25MB –MaxSendSize 25MB


Then at a Receive connector level


The message size limits on a send connector can be set through the Exchange Management Console via Server Configuration > Hub Transport by opening the Properties of the Receive Connector in the Receive Connectors panel:



You can also use Get-ReceiveConnector:



The default maximum receiving message size for receiving messages for Exchange 2007/2010 receive connectors is 10 MB. If you want to be able to receive larger messages over this receive connector, you can use the EMC or Set-ReceiveConnector:


Set-ReceiveConnector –Identity “MAIL1\Default MAIL1” –MaxMessageSize 25MB