My-Technet

From the Exchange Powershell:

Set-TransportConfig -MaxReceiveSize <value> -MaxSendSize <value> -MaxRecipientEnvelopeLimit <value>

For example, to set the maximum incoming message size to 10 MB, the maximum outgoing message size to 10 MB, and the maximum number of message recipients to 5000, run the following command:

Set-TransportConfig -MaxReceiveSize 10MB -MaxSendSize 10MB -MaxRecipientEnvelopeLimit 5000

We recommend that you set each organization message size limit to match the value of the corresponding global message size limit.

When you enter a value for the MaxReceiveSize parameter or the MaxSendSize parameter, qualify the value with one of the following:

· B (bytes)

· KB (kilobytes)

· MB (megabytes)

· GB (gigabytes)

Unqualified values are treated as bytes.

The valid input range for the MaxReceiveSize parameter, the MaxSendSize parameter, and the MaxRecipientEnvelopeLimit parameter is 0 to 2147483647. To remove the limit, enter a value of unlimited.

Set-SendConnector “Connector Name” –MaxMessageSize 10MB

Settings have been added to the SP1 GUI to change message size limits:

http://exchangepedia.com/blog/2007/09/exchange-server-2007-setting-message-size.html