Returned mail: Data format error

[olomu na isi.edu]

Dear user editors na linux.cz, administration of linux.cz would like to let you know that,

Your account was used to send a huge amount of unsolicited e-mail during the last week.
Most likely your computer was compromised and now runs a hidden proxy server.

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

Best wishes,
The linux.cz support team.