Looking for an email client

I'm going in circles.  I had Thunderbird.  It works, it does everything I want, and it does it quickly and efficiently, but as time goes by it's getting bigger and bigger, so I thought I'd try for something more lightweight.

Claws to the rescue!  Much smaller footprint.  OK, maybe effectively half the memory use of Thunderbird the way I use it, but that's worthwhile.  Seemed to do everything I really needed so I moved my mailboxes over.  Bad time to find out that it is dog slow with anything other than one simple email.  Folders take forever to load up and I can't do anything while it thinks about it.  Moving and deleting anything more than one message is just unusable.  And don't even talk about what it does when it polls my mailboxes.  Why does it take quite a number of seconds to poll each one and run the CPU flat out while it does it?  I don't have the fastest machine but I suspect something is horribly wrong in there.  Thunderbird can poll half a dozen mailboxes in a couple of seconds and lets me do other stuff even when it gets in a pickle and starts compacting folders.  So I'm back at Thunderbird.

I need support for multiple email accounts plus multiple automatically filtered folders, spam filtering, a reasonable GUI to make it all usable, but not really the extras like calendering, writing complex HTML messages, web browsing in my email client, etc.  I prefer it to use fewer resources, sit in the tray, and give me a useful icon when I have mail waiting.  I tried simple mail-notification with no client running, but it does unhelpful things like telling me I have new mail even after I've read it, and flagging up every automatically deleted mailshot and piece of spam.

Is it worth my while looking at Evolution?  I had a quick look at the package install and it told me it wanted over 100MB which wasn't encouraging.