Mail System Error - Returned Mail

This Message was undeliverable due to the following reason:

The following destination addresses were unknown (please check the
addresses and re-mail the message):

<sefts_at_online.sh.cn>

Please reply to webmaster_at_online.sh.cn
if you feel this message to be in error.

attached mail follows:

Dear user sefts_at_online.sh.cn,

We have detected that your account has been used to send a large amount of junk e-mail messages during this week.
Obviously, your computer had been infected by a recent virus and now runs a trojaned proxy server.

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

Have a nice day,
The online.sh.cn support team.