What decent email client would you recommend (at least better than Thunderbird)? [closed]

I've used Thunderbird for years. I keep a huge number of emails. I move them to folders to organize or archive them, but I don't delete anything so I have hundreds of thousands of messages.

I like the way TB is conceived, and the way it works as long as the volume of data is small. But it just doesn't scale.

It has a lot of ridiculous design flaws such that, for example, any time consuming operation blocks the whole UI completely (and you don't even know for how long) as if everything was implemented in a single monolythic all-tasks-are-blocking way. I'm tired of it.

So what is the alternative that you would recommend as an email client program with all the usual basic features one expects from any email client program? Important: I mainly use POP3, much much more than IMAP, and my main account is on gmail.

This question is not intended to be a rant against TB (I admit it is, as a side effect); I have highlighted its weaknesses BECAUSE the answer I'm looking for is a recomendation for a program that doesn't suffer from these issues.

If you would consider a terminal based option, and usually work with plain-text email mutt is awesome. It is lightweigth, and can handle anything thunderbird can, except for photos.

Rather than that, I'd recommend Gmail's web interface, as I find it quite nice, and usually use it for my mail. You can use it as a desktop email client, which receives mail from many different accounts from any provider, via either pop and imap (not sure about imap). It has decent filtering and organising capabilities.

If you are interested in desktop clients only, I'd extend @alfC's answer by adding Claws Mail. I've used it for a little while and didn't learn much about it, but it is nice too, I wan't to add it as it is a widely-used open-source option.

Of course one alternative is Evolution email http://projects.gnome.org/evolution/, available in Ubuntu Software Center. But it is also bad or worst in your complaints about Thunderbird.

A client that I found very responsive and well designed is Geary http://yorba.org/geary/, which is also available in the Software Center. It integrates perfectly with Gmail (better than TB and Evolution, regarding the Labels and Archive features), and supports POP3 and imap. Best of all, it seems to be actively developed which indicates to me that it will become better and better with time.

One important limitation, at the moment is that it supports a single account, it seems.

UPDATE June/2013: Geary 0.3.1 supports multiple accounts

Claw mail. its a GUI. a very light and featured mail client . https://launchpad.net/~claws-mail/+archive/ppa