How do you stop the "Default SMTP Virtual Server" from sending bounce messages for email addresses that you don't have?
i.e. I'm using IIS' SMTP server to handle my email and if an email is sent unknown at mydomain.com a bounce email with 'address not known' (or something like that) is sent back to the sender. I want it to silently fail.
This isn't an IIS failure. The SMTP server receiving the message is looking for a valid email address, and when it doesn't find one, sends an email back to your email address saying that there isn't one there. The only way to have it silently fail is by putting the from address as a bogus email like [email protected], etc.
From an SMTP point of view, a better way to handle this is to reject the RCPT request at some point during the SMTP transaction. This way, your server isn't responsible for sending any blowback to the alleged sender.
I don't know how to configure IIS to do this specifically, but you certainly can with Postfix (which is what I use).
I found this article which has a script you can run to configure a catch-all account on your server. All emails which would generate a NDR will instead be directed to this account. Sorry, I haven't tested it.
Basically the short answer to your question is no.
Brett
On another note, if you don't want to spend any money, or have no budget, and want a better email system, try something like Smarter Mail which you can use for free up to 10 users. I am sure there are others out there, but I have used Smarter Mail in the past successfully.