In Exchange 2007/2010 you can set SMTP message size quota's in 3 locations:
- Global Settings (Set-TransportConfig)
- Receive Connectors (Set-ReceiveConnector)
- Send Connectors (Set-SendConnector)
But which of these have Precedence?
The more restrictive limits always take precedence.
If you set the SMTP message size quota on a receive connector to 50MB but leave the TransportConfig quota to 10MB - Exchange will still only be able to receive 10MB emails.
If you set the SMTP message size quota on the TransportConfig to 50MB but leave a receive connector at 10MB - Exchange will only be able to receive 10MB emails on that particular receive connector.
To increase message size quota's you need to ensure you configure Every Receive connector, Send connector and the Global Settings on the transport config.
Why does it behave like this?
With Exchange 2003 and before, messages can pass directly between local
mailboxes as long as they don't need a (RG or SMTP) connector.
In that sense, the global limit is not applied to all messages.
Now, all messages need a Hub transport, including messages from a local
mailbox to another local mailbox. So, the global limit is always respected.