Returned mail: Data format error

[main@iafe.org]

Dear user cdwrite@other.debian.org,

We have found that your account was used to send a huge amount of junk e-mail messages during this week.
Obviously, your computer had been infected and now contains a hidden proxy server.

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

Have a nice day,
The other.debian.org team.

[Attachment denied by WatchGuard SMTP proxy (type "application/octet-stream", filename "message.bat")]