We set a limit of 25Mb on all Internet email (in and out). To reduce the load on our GWIA (which has its own domain) I've set a domain transfer limit of 25MB from any other domain to the GWIA's domain. When someone tries to send an Internet email larger than 25Mb to the GWIA's domain they get the following message back:

Message cannot be delivered because administrator has enforced message transfer size limitation.

Sender: [sender proper name]
Subject: [subject]
Item Type: MAIL
Message ID: 4C7FDF4E.7E9:97:32404
MTA Name: ["from" GW domain]
Transfer Limit is 25600 KB
Message size 67920 KB exceeds Transfer Limit of the agent

While this makes sense to you and me, it apparently doesn't to the general population; that message almost always results in someone trying to resend the same message (my current record is 37 retries before she hit her account size limit). Is there any way that I can edit this message such that I can deliver it in more plain language, with additional verbiage? Or is this a hard-coded message that's not adjustable my me?