My situation is that I have to support only a few users for email. They are all employees. However, there are several that are on the road and need the ability to send/receive emails from their laptops. Needless to say, when on the road, they do not have static ip addresses. I know that I can enable Pop before SMTP and this will resolve the problem.

The question, is, what is the purpose of the Relay for the following Hosts/Domains box? How do I use this in conjunction with Pop before SMTP? Also, how do I stop spamming, but still allow the road warriors the ability to send/receive/relay emails?

And yes, I did search the forum, but due to the sheer volume of information, I could not determine what was correct and more importantly, why it was correct.

In simple terms (somebody can correct any obvious technical errors) POP before SMTP authenticates the user before allowing them to send mail through a server.
As long as the user has a valid account and corresponding password they can login and check mail and send replies etc. (99% of our users do not have static IPs)
You may need to add the domain to the list of relays (ie. relay mail for this domain) in the control panel

Your staff will generate errors if they try to send emails BEFORE checking their mail, as the server will not have authenticated them (ie. checked that they are allowed to access the server's mail facilities).

By enabling POP before SMTP with the limited list of domains to relay for you will effectively cutout the chances of a spammer using your server to SPAM the universe.

There are a few tools around (try Google for the latest list) that can help you check if your server is vulnerable to spammers (open relay)
Hope this helps (hope it made sense and was acurate!)

couldn't you just install webmail?