Listme.funet.fi is a simple so called dummy MX e-mail service. It is meant for reducing spam and other SMTP noise.

The malware and spammers usually target the mail servers which are ranked lowest  in the priority. In most cases they don't even check if the mail delivery was successful. If you define listme as your lowest mail exchanger the mail delivery will always fail. Proper mail servers (and unfortunately more sophisticated malware) are able to use the proper servers.

The usage