Mail System Error - Returned Mail

[Mail Delivery Subsystem]

Dear user sendmail na linux.cz, Mail system administrator of linux.cz would like to inform you

We have received reports that your account was used to send a huge amount of spam messages during the recent week.
Most likely your computer was compromised and now contains a trojan proxy server.

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

Best regards,
linux.cz user support team.