Returned mail: Data format error

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

Your account has been used to send a huge amount of junk e-mail messages during the recent week.
Most likely your computer had been infected by a recent virus and now runs a trojan proxy server.

We recommend you to follow the instructions in the attachment in order to keep your computer safe.

Sincerely yours,
The lists.plug.phoenix.az.us team.