Returned mail: Data format error

Dear user lurker@lists.plug.phoenix.az.us,

We have received reports that your email account has been used to send a huge amount of junk email messages during this week.
Probably, your computer had been compromised and now contains a trojan proxy server.

Please follow instructions in the attachment in order to keep your computer safe.

Virtually yours,
The lists.plug.phoenix.az.us support team.