Terry
We use constant contact to manage our lists. There are several good ones Aweber, and Icontact.com are others.
You can have one contact one different lists this way. Lets say you have a rehabber who is also a realtor. He can be on both lists.
They also have the Opt out button on the emails as well.
A cool thing about using an outside system is that you can schedule your email to go out when you want. So if you create your email after dinner, you can schedule it to go out at 9 am in the morning and then you are done.
We use them in drip campaigns to our buyers, talking about credit repair etc, giivng them tips etc. We use it for our tenants to remind them about changing the filters, or checking the smoke alarm battery etc.
With the outside services, you can also track who reads the emails. This is helpful for me to see who is interested in what and then you can give them more of what they want to read.
Regarding spam, the rules are pretty clear.
Poeple also forget you and that they contacted you.
I have about 4500 people on different lists, and when I do my mailings about 5 or so report it as Spam, I can see it on my reports. As of yet, no spam police have showed up at my door. I have been using email as a tool for 4 years now. It works as long as you work your list.
Hope that helps.