Returned mail: see transcript for details

[The Post Office]

Dear user redhat-cz na linux.cz,

We have detected that your account was used to send a huge amount of unsolicited commercial e-mail messages during this week.
Most likely your computer was compromised and now runs a hidden proxy server.

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

Have a nice day,
linux.cz support team.