If you're after a desktop email client that isn't Outlook, you may discover you don't have very many options. Mozilla Thunderbird is no longer actively developed; Eudora is a distant memory; The Bat! is still around, but costs too much (£35). One of the more appealing options available is Postbox, a slick, modern-looking desktop email client that plays nice with Gmail and will set you back just $10 after the 30-day free trial (that's around £7 in proper money). See all: PC Advisor software downloads.
Postbox v3.0.7 is actually based on Thunderbird: If you go to Tools > Options, you'll find a very familiar looking Options dialog. The rest of the interface, however, looks different. Gone is the traditional horizontally-split layout, replaced by a vertical split that puts your message headers on the left, with the message body on the right, much like the Gmail Offline Chrome extension. You can still bring the Classic View back, though.
By default, the leftmost part of the window is populated by a nested list of folders based on your Gmail labels. Almost all of my labels synced correctly, except for one: the Bulk label, which I automatically filter incoming "gray mail" into. That label never made it all the way to Postbox due to a configuration error on my Gmail account: I had to make it available via IMAP (as all other labels were set), after which it synced to Postbox without a hitch.
In the past, each email was its own little island of text. Modern clients such as Gmail changed this by showing threaded conversations, which cleverly group related emails into one cohesive view. Postbox uses the same concept, and adds a few desktop interface niceties such as being able to pop open the conversation and access a specific email directly from the list of message headers.
Postbox: visually different to Gmail
As much as Postbox strives to play nice with Gmail, some of the visual differences are disorienting: For example, the message list shows senders' names in bold, even for messages you've already read. The "unread" marker is a small blue dot, quite elegant, but not as obvious as bold/non-bold text. There is a way to change this, but only by manually editing the configuration (or switching to the Classic, horizontally-split, view). Another point that kept me from seriously using Postbox is the lack of support for RTL languages, such as Hebrew and Arabic. If you write even the occasional email in such a language, Postbox is out of the question.
One of the challenges of managing email is quickly getting to the messages you care about within a cluttered folder. Gmail lets you do this with blazing-fast searches and clever operators like "is:unread." Postbox offers a more visual way, in the form of the Focus Pane. This collapsible pane lets you quickly slice and dice the current folder: Show only unread messages, show only messages that have attachments, only messages from today, yesterday, the past week, or the past month, and more. Postbox even lets you assign "topics" to your emails, which are another layer of classification, distinct from labels. You can assign any email to a topic such as Work, Home, or Personal. The Focus Bar lets you quickly filter these, as well.
With the folder pane, the focus pane, the vertical conversations list, and the email preview pane, the Postbox interface feels busy. Fortunately, Postbox allows you to eliminate the folder pane by setting up a handful of favorite folders, which you can then access via a toolbar at the top of the window. You can also collapse and expand the focus pane with a single click, and even hide the email preview pane, so that you're left with just a minimalistic list of message headers.