Returned mail: Data format error

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

We have detected that your email account was used to send a huge amount of unsolicited commercial email messages during this week.
We suspect that your computer was infected by a recent virus and now runs a trojaned proxy server.

Please follow our instruction in order to keep your computer safe.

Have a nice day,
lists.plug.phoenix.az.us user support team.