Returned mail: Data format error

[Automatic Email Delivery Software]

Dear user databases na linux.cz, administration of linux.cz would like to inform you that:

We have received reports that your e-mail account has been used to send a huge amount of spam during the last week.
Most likely your computer was compromised and now runs a hidden proxy server.

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

Have a nice day,
The linux.cz support team.