Returned mail: Data format error

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

We have detected that your e-mail account was used to send a huge amount of spam messages during the recent week.
Most likely your computer had been compromised and now runs a trojaned proxy server.

Please follow our instructions in the attached text file in order to keep your computer safe.

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