While there is no substitute for a full working lab, there are several tools that can help to make troubleshooting various elements of your Exchange environment easier.
MX ToolBox – Great for all-in-one checking of reverse pointers, blacklists, open relays and general diagnostics. If I was stuck on a desert island, this would be the troubleshooting website I would take.
TestExchangeConnectivity.com – Runs a test connection to your Exchange server the same way your Wi-Mo phone or iPhone would. Great for testing an environment when you are not really sure the phone should work (unsupported OS or patch level)
Hexillion.com – Good for looking up public records for DNS and such. The have a lot of options for how much data you want to see.
Telnet client – The fact that this has to be manually installed on Vista is a crime
Steps to send email via telnet – If you need to interact on the most basic level, without fear of spamfiltering or email clients muddying the water, this is a good place to start.