Can SpamAssassin be set to junk all emails sent to multiple recipients

I would like to set SpamAssassin to junk all emails sent to multiple recipients. Ideally it would be only emails with say approximately 4 or more recipients in the "To:" field.

If SpamAssassin could bounce them, that would be even better.

I don't care if it junks emails from individuals as well as from spammers.

I've read the documentation that John-Paul kindly suggested; but I couldn't find anything that looked as though it would do it. If it is possible to do this; please can someone tell me how to do it. Many thanks.

Thanks