Incredimail is really just a funner version of MS Outlook Express or Eudora, e-mail programs you use directly on your computer. What they do is relay your messages from other sources, either the web or otherwise, and store them on your computer for you to view. What I like about using a program like this is that I can check all my email accounts without having to log in to so many different places. It's compatible with hotmail and any email addresses you may have signed up for with your ISP (internet service provider), as well as the UK version of yahoo mail (the US mail accounts require a fee to use POP forwarding services).
To try it out, or to use the free version of IncrediMail, visit the site by clicking here and trying out the demo or downloading the free version. I liked it so much after trying it for a while that I bought mine!
The letters here refer to the message backgrounds. Now I know what you're thinking, not all e-mail accounts show the same images or allow for backgrounds and fancy shmancy html. You're absolutely right, some of these letters won't display properly in yahoo inboxes or hotmail inboxes, but they will display in an incredimail browser. So in effect, if you send something via incredimail to a friend who also has incredimail, they'll see the exact same thing you sent them. On the other hand, most email accounts will recognize the embedded images and will still display them, even if the background, or the color of the text are overridden.