Best way to whitelist mailing lists

I'm trying to whitelist some mailing lists and running into a regular
problem.  I usually use Env_From to whitelist, as is used extensively in
the whitecommon file.  However, I have lots of mailing lists which look
like this:

	env_From: <crypto-gram-return-54-tim=meer.net@chaparraltree.com>

I was wondering if it would make more sense to use the 'HELO' field or
the IP address (if it's a regular mailserver and not a chain of them). 

thanks

tim