Suggestions for mail client

Hello.

I've been a progressively unhappier ThunderBird user for almost the last 
20 years; the upgrade to 115 brough a general slowness (with specific 
big troubles in some areas), but I resisted.
Unfortunately 128 is truly unusable: moving from one folder to another 
or from one message to another takes seconds (so just skimming the 
messages on FreeBSD mailing lists is now taking tenfolds the time it did 
until a week ago), resizing the message pane takes about 5 seconds, 
marking 50 messages as read takes close to one minute, etc...).

Don't get me wrong, I still like ThunderBird (altough with a lot of 
criticism), but unless there's a compiler switch (LTO?) or something 
else that can bring TB back to the speed it had a couple of years ago, 
it's time to move on to something else.



In the port tree I see Evolution, Geary, KMail, Sylpheed and possibly 
others I might have missed.
I read several comparison but came up with no clear winner; of course I 
could try them all, but it would take days of work.
So I'm asking here for a suggestion...


What I absolutely need:
_ close to perfect IMAP support;
_ IMAP tags/labels;
_ multiple accounts: I've got more than 50, although I use less than 10 
daily and I could leave the other 40 in ThunderBird for occasional use;
_ online only/no local storage (for some accounts) *and* local cached 
messages (for others);
_ support for big folders (in the GBs size and or 10k messages);
_ CardDAV support;
_ good searching;
_ performance, stability, future support, etc...

What I'd like:
_ newsgroups support;
_ RSS;
_ CalDAV (these three I could eventually achieve with other programs, 
still...):
_ possibly not locking in into some desktop environment (currently I use 
XFCE);
_ ability to read HTML mail (altough I never write such a thing).

What I don't care about:
_ message filters;
_ antispam (as I manage them both server side);
_ "modern" interface.

Any hint?

  bye & Thanks
	av.