Why do you want to whitelist an entire domain?  Whitelisting anything is extremely dangerous!

Whitelisting is not on a domain.  It is on the SMTP servers that transport mail for that domain.  You need to find the IP addresses that Craiglist uses, and whitelist them.  I wouldn't do it, but that's what you asked.

 

Note that if you could whitelist a domain, then any spammer could simple spoof a Craigslist address and put all the spam they want in your inboxes.  Don't think your users would be too happy with that.  

Thanks guys.

Rod, I did what you suggested and put them in as a Trusted Sender. That is what I was trying to do, stop them from being treated as spam.

 

Regarding whitelisting a domain as bad... True, but whitelisting an IP address then is even worse !  If you whitelist a domain, then anything from that domain comes through, but as its set up now, you have to whitelist an IP address. Meaning "BillyJo-JimBob" web hosting service has 4,000 domains on it and all of them share the same IP address as a mail server.  all 4,000 could spam you and they get through if you whitelist that one IP.  I would much rather take the chance with a single domain than an IP address.