I have created a variety of systems in my email provider's auto-responders to keep in touch with customers. It took quite a bit of time and thought, and I'm proud of my work!
I recently was able to review The Client Angel and I think that it is a perfect solution for direct sales professionals. You can use as much or as little of the functionality as you like. At the least, it's an email database. At it's greatest potential, you have full-fledged CRM (Customer Relationship Management)
When I worked in the marketing department of an international consulting firm, I was part of the Siebel Sales Database installation. That project was hundreds of thousands of dollars and thousands of man hours. This program brings the integral parts of CRM to the WAHM or entrepreneur at a very affordable price.
At the time of this writing, the cost for up to 250 clients is $4.95 for the first month and $15.00 for the following months. Larger plans are available.
Full Disclosure: The links included here are affiliate links. If you choose to use this service, I will receive a portion of the sales price. I was not paid to endorse the product, all opinions are my own and given freely.