Gmail and Yahoo Mail are both web-based mail programs, but the Droid 2 includes special software that lets you use them without having to visit the Web—just use the specific app on your Droid 2. But there are other web-based mail programs out there, including the very popular Hotmail. You can use just about any email service on the Droid 2, and most likely very easily. Visit the site with your web browser, and you should be able to use the email site just as if you were using it on a computer. In some cases, when you visit the site, you’ll be automatically routed to a site specifically built for smartphones, so that all the features are formatted nicely for your phone.
In some instances, there might even be an app you can download from the Android Marketplace, or from the Web, that you can use instead of a web browser. Search the Android Marketplace (Using Market) to see.