Eudora users face a great decision by Qualcomm – Eudora goes open source from first half of 2007!
You could read more at the official web site.
Eudora is a great mailer program, and now that it goes open source, it hopefully will add some more details, which were missing – e.g. cyrillic alphabet support. What makes Eudora better than usual mailers (e.g. Outlook Express, or Outlook), is that it allows usage/moving/copy of your mail without problems via different computers. For example, if you get a new PC, you don’t need to worry – you can copy all your mailboxes, filters and configuration files on the new compter, and they will work just fine, without any problems.