Since I converted to Macs five years ago I've been reasonably happy with Apple's Mail OS X app. It does everything the average user needs and offers superb integration with MobileMe, but it is not as powerful as Outlook, for instance. I've tried a number of alternatives but nothing has come close to Postbox which I have now adopted as my main mail program. I read this in-depth review on AppleReviews.com and immediately downloaded the 30-day free trial.
I was impressed by the quick and fuss-free way in which Postbox imported all my mail accounts. All I had to do was manually re-enter the passwords (which is a useful precaution) and I was up and running.
Postbox, which is based on Thunderbird, majors on a fresh, Mac-like interface and extended search facilities. For the power user it is a viable alternative to Outlook while retaining full Mac compatibility and integration with MobileMe. Features such as tags, filing options and quick-reply panes from within an incoming message enhance productivity. The sidebar for accounts and folders differs dramatically from Apple's unified design. In Postbox, accounts are separated from the list of folders. I find this more intuitive and less cluttered. In addition, there is a separate pane to the right of a message which collects all attachments and imagines in one place.
Right: The accounts and folders bar is arranged more logically than in Apple's unified design
The customisable threading facilities are a quantum leap from Mail's rather basic skills. Postbox has the capability to gather incoming and outgoing mail within a single thread so you can follow a conversation rather like you would a SMS thread on the iPhone. On opening the latest message you find all previous correspondence collapsed below the text so you can see exactly what has gone on before. I love this feature. But the quick-reply option from within an incoming message is my favourite. Pressing the quick-reply button opens a small window within the message where you can type a response without the need to open a full reply pane (which, of course, you can still do if you wish).
Postbox works on a browser-style tabbing system which most users will be familiar with and will quickly adapt to. Instead of messages opening in a new window they appear as tabs. Inbox is usually the left-hand tab and you can open as many messages as you like without cluttering the screen. This works especially well when screen size is limited as, for instance, on the 11-in MacBook Air.
After two weeks of putting Postbox through its paces I'm now addicted – just as I am to BusyCal which enhances iCal in much the same way – and I would recommend a 30-day free trial to any reader who wants a bit more than Mail.app offers.
The screenshot below (acknowledgement to the Applereviews feature), shows the conversation thread view in Postbox. Note the tabbed windows, similar to Firefox, the radical folder structure on the left and the unified attachments and images pane on the left. In the main message you see how conversations (which can be collapsed to headers) are threaded in a very easy-to-follow way.