I'm looking for a good, lightweight email client

I'm looking for a good, lightweight email client.

What do you guys recommend?

Popular email clients for the Mac include:

• Apple Mail - my current favourite, especially in Lion.
• Postbox - Paid for, but feature-rich and quite polished AFAICT
• Thunderbird Free and open-source. Extremely configurable with a similar extension ecosystem as Firefox.
• Microsoft Outlook - A very fully featured email and calendar package. It replaces Microsoft's previous Mac email client, Entourage.
• Sparrow - A unique email application. The layout encourages casual, Twitter-like conversation by evoking the timeline view of popular Twitter apps. It's pretty trendy at time of writing.
• Mailplane - Basically an optimised, dedicated Gmail browser window. Worth looking into if you're a heavy Gmail webmail user.
• MailMate - I hadn't heard of this one before, but it has a good review at Lifehacker.

Apple Mail. Nothing is as integrated into the OS as apple's own mail. Works seamlessly with Gmail