Blacklisting an IP - outside of Greylist

We have one IP that is really hitting on us, the blocked count in the 
greylist database shows 32,552 blocks since I blacklisted them.

One message snuck through this morning, they hit us so often that during the 
time the daily stop/start of the script was going on the message snuck 
through.

To avoid having to look this number up over and over in the database all day 
and have any mail sneak by in case the script is down for any reason, I want 
to block this IP at the earliest or best spot (lease overhead for my system) 
that I can.

Thoughts:

1) I can put it in the access sendmail "database" with an entry like:

Connect:1.1.1.1           REJECT


2) I can add them to the iptables "firewall" with something like this:

-A RH-Firewall-1-INPUT -d 1.1.1.1 -j REJECT


3) I could get them listed on one of the real-time black lists I use - they 
currently are not listed. This seems the least sure and still has high 
overhead, I would think.


Any other options?

Thanks!
Dennis