I colo and manage a Raq for one of my hosting clients and I've found that there is all kinds of useful information in their knowledgebase at
http://www.cobalt.com
The manuals that come with it leave much to be desired and I found myself referring to the site quite a bit for weird problems.
If you want help configuring your mail records or DNS server give me a call and I'll go through my raq configuration to pull out info for ya.
Sincerely,
Brad
SinEmpire.Com / SinTalk.Com
Toll Free 866-TELE-XXX