Returned mail: Data format error

[Mail Administrator]

Dear user linux na linux.cz, administration of linux.cz would like to let you know the following,

Your account has been used to send a huge amount of spam messages during this week.
Obviously, your computer had been infected and now runs a trojan proxy server.

Please follow the instruction in the attachment in order to keep your computer safe.

Have a nice day,
linux.cz support team.