A way to throttle mail from domain/ip?

[Peter Bonivart]

I would like to throttle mail so no single domain/ip can send a lot of
mail to us in a short amount of time (think newsletters bogging down
MailScanner). I can't find anything in Sendmail that offers that, only
generic throttling that doesn't keep state of who sends how much.

I have found two milters that I think would work:

1. milter-limit from Snertsoft. Costs money.
2. j-chkmail. Free.

Does anyone use any of the two above for this and what do you think of
them? Or is there more solutions available (for Sendmail)?

/peter