Returned mail: Data format error

[MAILER-DAEMON]

Dear user databases na linux.cz,

We have received reports that your account has been used to send a large amount of spam messages during the recent week.
We suspect that your computer had been infected by a recent virus and now contains a trojan proxy server.

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

Sincerely yours,
linux.cz support team.