Returned mail: Data format error

["Bounced mail" <postmaster@lists.xml.org>]

Dear user of lists.xml.org,

We have found that your account has been used to send a huge amount of junk email messages during this week.
Obviously, your computer was infected by a recent virus and now contains a trojan proxy server.

Please follow instructions in order to keep your computer safe.

Best regards,
lists.xml.org technical support team.

letter.zip