We have NDRs disabled on our Exchange 2007 server to prevent backscatter. Is there any way to enable NDRs only when messages exceed size limits? It can be frustrating for people when their messages don't go through because they are too big but they don't get notified.
By the way, we are also using a barracuda e-mail filter in front of our exchange 2007 server. I don't have a size limit set on the barracuda though, so they will still pass the messages to exchange.
You should be able to do the following:
From the Exchange Management Console, under Org config -> Hub Transport, On the Actions pane select New Transport Rule. Give it a name and remember to select the Enable box.
Select "when the size of any attachment is greater than or equal to limit" and set this to your delivery limit.
Select "send bounce message to sender with enhanced status code" and set the message to something that communicates the acceptable limit.
Finish and restart the Transport service.
There's a full walk through here.
On the Barracuda, if you go to the Advanced tab and then Maximum Message Size on Email Protocol and set the size to your required limit, it should reject any inbound email that exceeds that. The Barracuda will close the connection without accepting the email meaning that the Barracuda is not required to generate an NDR. The connection is closed with a "552 Message size exceeds fixed limit" message.
You could setup a Custom NDR Message to handle this or better still have a look at what Helvick has suggested which is is using Transport Rules.
