Mail server report — no, a robot didn't really detect abnormal activity from your IP address

Just received two identical copies of this from from the same sender in the Czech Republic (but with different "From" lines):

Dear Customer,

Our robot has fixed an abnormal activity from your IP address on sending e-mails.
Probably it is connected with the last epidemic of a worm which does not have patches at the moment.
We recommend you to install a firewall module and it will stop e-mail sending. Otherwise your account will be blocked until you do not eliminate
malfunction.

The enclosed zip file is, of course, a virus of some sort. If you're reading this, you're probably smart enough not to fall for it, but you should probably tell your more trusting friends and relations to ignore this email when they get it.