Answer
Free Windows Email Applications
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Mozilla Thunderbird – http://www.mozillamessaging.com/en-US/thunderbird/
Windows Live Mail
(Is intended to be a successor for Outlook Express on Windows XP_
and Windows Mail on Windows Vista). The first version was V12.
Eudora (Sponsored Mode) – http://www.eudora.com/download/
Opera – http://www.opera.com/download/
Mulberry – http://www.mulberrymail.com/download.shtml
(Open source)
Pegasus Mail – http://www.pmail.com/downloads_s3_t.htm
IncrediMail – http://www.incredimail.com/english/download/
Foxmail – http://www.softpedia.com/get/Internet/E-mail/E-mail-Clients/Foxmail.shtml
(Above link is via a third party site. Currently no IMAP support)
DreamMail – http://www.softpedia.com/progDownload/DreamMail-Download-79083.html
(Above link is via a third party site. Currently no IMAP support)
Alpine – http://www.washington.edu/alpine/acquire/
Sylpheed – http://sylpheed.sraoss.jp/en/
i.Scribe – http://www.memecode.com/scribe.php
Mozilla SeaMonkey – http://www.seamonkey-project.org/
Free Mac Email Applications
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Mac OS X Mail – http://www.apple.com/downloads/
Mozilla Thunderbird – http://www.mozillamessaging.com/en-US/thunderbird/
Eudora (Sponsored Mode) – http://www.eudora.com/download/
Opera – http://www.opera.com/download/
Mulberry – http://www.mulberrymail.com/download.shtml
(Open source)
Mailsmith – http://mailsmith.en.softonic.com/mac
Alpine – http://www.washington.edu/alpine/acquire/
Free Linux Email Applications
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Evolution – http://projects.gnome.org/evolution/download.shtml
Mozilla Thunderbird – http://www.mozillamessaging.com/en-US/thunderbird/
KMail – http://userbase.kde.org/Kmail
Balsa – http://balsa.gnome.org/
Sylpheed – http://sylpheed.sraoss.jp/en/
Alpine – http://www.washington.edu/alpine/acquire/
Keywords:POP3 client email