Handling Bogus Domains using SMTP Connectors in Exchange

Talking about SMTP Connectors in an earlier post got me to thinking of another way we use the SMTP Connectors in Exchange.

A client has a (horribly behaved) legacy piece of software that, when faced with a customer with no email address on file, sends an email to an address it makes up in a legitimate domain. So, for a long time, they were bombarding this innocent third party domain with mail that was destined to go nowhere.

This was eating bandwidth, processing cycles and the like, so we tried to put an end to it by appealing to the developers. They were not interested in fixing the old program, it would continue to spit out its bogus mail.

We created an SMTP Connector in Exchange to handle delivery to the legitimate domain. (It should be noted that the domain probably wasn’t legit when the program was written, but with the .com explosion, it became legit. It’s also not a domain anyone would be sending mail to in the normal course of business… it’s not like this is for AOL.COM or anything…)

We set the connector so in the “address space” we listed our desired domain. We checked off “Forward all mail thru this connector to the following smart hosts”

… and this is where we get tricky …

… we put a non-routable IP address in the smart host field. (And remember to enclose the IP address in brackets – i.e., [] )

On the Delivery Options tab, when it asks when it should deliver, we tell it to “Never Run”

And that does the trick. We no longer pester the legit domain, we don’t eat any bandwidth, everyone’s happy.