Postbox is an email client that attempts to take the best features of Thunderbird 2.0 and Mail, synthesise them and give the best possible mail client around.
Postbox certainly has a long list of useful features, as well as a beautifully polished interface. Conversation threading lets you view lengthy email exchanges grouped either in the inbox or in a separate palette. Quick access to all the links, attachments and images embedded in emails is available in palettes and sidebars.
Two different types of tagging let you categorise messages for easy filtering. Facebook and Twitter integration lets you pull in profile pictures for contacts; To Dos let you prioritise emails.
Some Thunderbird third-party add-ons work and Thunderbird 3 features such as tabbed browsing and OS X Address Book integration are also present.
Unfortunately there's no unified inbox for all your email accounts, so you have to click between inboxes to see all your new mail. Plus there's no support for Exchange accounts, and no Time Machine or iLife integration. Thunderbird's advanced features are MIA, too.
Junk mail handling is poor and there's no way to improve it with SpamSieve. The application does provide an assistant to import accounts and messages from Mail and Thunderbird.
However, a Yahoo POP account imported directly from Mail never displayed any messages, even when there were over 40 dwelling on the server.
Postbox is tempting, but what you gain is offset by the things you lose.
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