Questions about windows client features

I need a new windows email client. I've been using Eudora 3.01 for
10+ years.

Feature needs:

1. Use lists to send out in which the actual recipients in
"To:" =
Mary Jane
John Smith

instead the horrendous "whole list" included
or some title like "My colleagues"

My limited reading in these ngs is that Pegasus
works with simple text lists of addresses but does
not give the single actual recipient after "To:"
Can anyone clarify this?

Poco/Barca is evidently good with lists like this, but
I'm a bit leary about the program's stability.

2. Good text/content searching on individual folders/mailboxes.
Eudora has always annoyed me with insisting on searching
the whole shebang from the beginning...and then now highlighting
what you're looking for. And - of course - once you're there,
you can't search for it!

3. Receiving formatted html, if that what the message is.

4. Good script security.

So far - not in any order - I'm considering
Pegasus
Barca
Mozilla Thunderbird

But I can't adequately discern how well these apps meet
the above needs.

Any help will be greatly appreciated.

--
George Newton