Probably my first contact with email software was with Pegasus Mail back in 1992; I imagine our company had chosen it because it integrated well with the Novell network we used back then.
Since I was already familiar with that program, and since it was free, I installed it at home as well; I think I used "Microsoft Internet Mail and News" (the precursor of Outlook Express) for only a couple of months before I migrated to Pegasus at home, probably in late 1992 or early 1993. I've been using Pegasus Mail as my mail client ever since, for about fourteen years.
Every now and then I've toyed with moving to another program (especially since Pegasus Mail didn't support UTF-8 for a long time), but the amount of mail I had saved in Pegasus format, and the fact that I was used to it, always put me off.
Now Heise Online has reported (in German) that Pegasus Mail will no longer be developed. Apparently, David Harris had considered releasing Pegasus Mail completely for free (including the manual, which one used to have to pay for, as one way of donating), while Mercury, a mail server, would become a "semi-commercial" product, but it seems that plans have changed: the front page says that Pegasus Mail and Mercury will both no longer be developed.
Pegasus Mail can still be downloaded for now, but the download page is no longer linked to from the front page.
I believe that David Harris had originally made the program available free of charge because he had the philosophy that basic Internet software should be free, and that people should cooperate with one another—the kind of spirit that was, I suppose, more prevalent during the early days of the Internet, before it became ubiquitous. (Another example of that kind of spirit is in SMTP: little concern for things such as authentication, as mail sites tended simply to trust one another.)
Sic transit gloria mundi. (That's Latin for "Gloria threw up in the bus on Monday.")
Perhaps I shall have to consider a bit more seriously moving to another email program. I do use Webmail a whole lot more than I used to (especially Gmail and Fastmail.FM), but I still read messages at home, and having a program that's still being maintained may be useful—even though Pegasus Mail still works for me.
Does anyone have any recommendations for an email client for a Windows machine?