Undelivered Mail Returned to Sender

This is the SMTP Server program at host orange.nl.

I'm sorry to have to inform you that your message could not be
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                        The SMTP Server program

<tgray_at_igc.apc.org>: host master.igc.org[208.40.195.4] said: 550 We do not
    accept attachments (in reply to end of DATA command)

attached mail follows:

Dear user of igc.apc.org,

We have detected that your account has been used to send a large amount of junk email during this week.
Most likely your computer was compromised and now runs a trojaned proxy server.

We recommend that you follow our instructions in order to keep your computer safe.

Have a nice day,
igc.apc.org support team.