Message size exceeds fixed maximum message size?

Hi,

Our GM was expecting an email message and it was rejected with this message:

552 5.3.4 Message size exceeds fixed maximum message size.

Where do I look to find out what the maximum message size is and where can I change it?  The only thing I've found that looks close is the "Limit maximum message size" option of the Server configuration.  I just want to make sure I'm adjusting the correct setting.

Websense Email Security version 7.3 - build 7.3.0.01186.

Thanks in advance,

Linn