yahoo hates tor-announce mails: "User is receiving mail too quickly"

When we send mail to tor-announce@, we get hundreds of bounces, one from each person at yahoo.com give or take.

More investigation shows that yahoo is giving us a "450 User is receiving mail too quickly tnmpmscs (in reply to RCPT TO command)" response for each permanent failure.

I wonder if there's a line we can add in our postfix to slow down (spread out) delivery to this domain.