[Mimedefang] Hot do I stop becoming a spam relay.

[Andrew Watkins]

Hi!
First of all my sendmail does not allow relaying, but I am now getting a 
lot of e-mail where email is sent to an unknown local user and then 
there is a BCC to some other location:
for example:
    From: spammer at domain.com
    TO:    XXX at ourlocal.domain.com
    Bcc:   someone at external.com

I guess the letter of the of the law I should deliver the e-mail, to the 
external address, since typo 's do happen, but there must be away round 
it. May be I could not deliver Bcc if the to address is invalid?

Any pointers....

Andrew