Here's a bit of a strange one:

I've got a client who has an email address that acts as the catch-all for their domain. She noticed that she had 632 emails within a 10-minute span late last night that were "undeliverable."

What I noticed about them is that they all came from things like (some random dictionary word)@(domain name). So they weren't anything anyone in the office would have used. So it's like a dictionary harvest attack, only the other way around.

The question I have is: is there any way to force users of a domain name to authenticate to it on the server side (the site's hosted on an NT server...I believe it's a Windows 2000 server, but I'm not sure because it's not my server) before emails go out? Thanks.

There is a big chance that it was sent from another SMTP so authintication wouldn't work in that case.

I'm with the Bill Gates fan here.

It's probably spam coming from the outside world. I get a lot of spam saying an email I had tried to send is undeliverable, only, I never tried to send that email. I really don't know what the point is, because it didn't have any viagra. Maybe spammers are sending out blankets and seeing which ones are returned undeliverable, and the ones that aren't they can assume are valid emails?

That's just it, Learning Newbie. In order for a spammer to see that they're undeliverable, the spammer would have to have a return address that could check for the bounce-back email. That's why this really doesn't make a lot of sense to me.

Anyway, I kinda figured this was the answer. I just wasn't sure if there was any method of authentication that would allow for this sort of tracking.

Ah well...what can you do? Stupid email.

Thanks, guys.