The Bat! 9.5 (64-bit)
A powerful email client with suppport for any number of POP/IMAP accounts, PGP encryption, spam filtering, custom mail filters, plugins etc: manage incoming email right on the server, toss messages from your friends into special folders, mark messages from your dear ones with special colors, send automatic replies, create virtual folders, use templates, and much more.
Note that The Bat! doesn't support embedded images in HTML email, that is, it won't download graphics embedded as HTML links (i.e. as "IMG SRC" tags in the email body); however, it does support images sent as attachments. The lack of ability to automatically download and show imbedded images can be a downside for some, but it will actually safeguard you against automatically downloading and executing malicious scripts posing as images: it is not widely known, but it is possible to embed a specially designed script inside an image file in such a way that some popular browsers and email programs will automatically execute the script once the image is downloaded.
The Bat! Professional Edition vs The Bat! Home Edition
For the Home Edition spell checker dictionaries can be downloaded separately, they are included in the International Pack. In the Professional Edition the dictionaries are a part of the standard installation file.
For the Home Edition the multilingual interface can be downloaded separately, thet are included in the International Pack. In the Professional Edition the multilingual interface is a part of the standard installation file.
Possibility for hardware authentication with mail servers.