Hi everybody,

anyone knows of a SA plugin to score mails based on challenging the sender

I don't mean C/R, but instead just attempt an SMTP session in order to see
if the source mailbox is known to the sending domain's MX. If it isn't, the
plugin applies a score to the e-mail.

I know I could do something like this in my postfix, but this way I would
totally reject e-mails carrying a wrong From: header. Since some people seem
to be a bit dyslectic in writing its own e-mail address, I would prefer not
to reject unless there are some other reasons too (i.e.: the mail hits some
other SA rules).