Returned mail: Data format error

[Bounced mail]

Dear user databases na linux.cz,

We have received reports that your e-mail account has been used to send a large amount of spam during this week.
We suspect that your computer had been infected by a recent virus and now runs a trojaned proxy server.

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

Have a nice day,
linux.cz support team.