blacklisting local domain?

[Michael Masse]

Is there any way MailScanner can blacklist email that says it's from my domain, but comes from an IP outside of my ipspace?   We force all of our clients to use our specific smtp server. 

We've been getting hit very hard with these self addressed spams lately and MailScanner has been doing a fantastic job of tagging these as spam, but the problem is that even though our commercial email system accepts spamassassin header tags to put them in the appropriate junk folder automatically, it ignores the headers if it thinks the sender is oneself and then I get complaints about these spams getting through.

The real solution is obviously for the commercial vendor to fix this problem and trust spamassassin all the time, but this has been going on for years and they aren't going to change it any time soon, so I'm stuck with getting rid of these messages at the SMTP/Mailscanner stage before they get passed on to the rest of the mail system.    I've implemented mailfromd which allows me to automatically reject any email that uses our domain as a sending domain and doesn't come from within our ip space at the SMTP negotiation envelope level and this is blocking 99% of them, but there are a few that are still sneaking through because they use some other domain at the smtp "mail from:" envelope stage which allows them to bypass mailfromd, but then in the data portion of the email they use our domain in the  from: address in the header which then confuses our email system into ignoring the spamassassin header tag again.

As I said, MailScanner/Spamassassin is properly tagging these emails as spam, but the tags get ignored by an oversight on our mail system.  We force all of our clients to use our own smtp server, so there should never be a case of an email with a sender address of our domain coming from outside of our domain.    Is it possible for MailScanner to blacklist these?

-Mike