[quote user="Goody"]So far, I have found only one client that does all this and much more.  The only thing is HTML seems to get it problems.  HTML must be a difficult thing to process in email clients.[/quote]

It's difficult in and of itself. One of the problems is that HTML parsers, unlike XML parsers, are designed to be "forgiving". XML parsers are supposed to stop parsing when encountering syntax errors:

[quote]Second, XML has draconian error-handling rules. In contrast to the leniency of HTML parsers, XML parsers are required to fail catastrophically if they encounter even the simplest syntax error in an XML document.[/quote]

http://webkit.org/blog/68/understanding-html-xml-and-xhtml/

I guess the web would not have grown as phenomenally fast as it has if the people who coded web browsers hadn't tried to be lenient in their parsing, working around errors and trying to second-guess what someone had "meant" when he made an error in his page. It's meant anyone and everyone can put up something written by hand in a slapdash suck-it-and see way in Notepad or in poor WYSIWYG tools that write dodgy HTML. And there's a kind of vicious circle here.

But the result is that HTML parsing is a bit of a mess. How should a browser handle some error that someone should not have made in the first place? It's anyone's guess, and the error-handling of every browser is different. Should you give someone what he's (literally) asked for when that makes no sense, or guess that he's got a conceptual misunderstanding here that's not uncommon, and that Internet Explorer has made allowances for, so that you'd better do the same? It makes browsers even more complex than they need to be and even larger. Have you seen the size of Firefox these days? And don't even ask about Internet Explorer.

There's also the matter of proprietary extensions to the HTML standards--though that's perhaps less of a problem than it was. However, it's certainly a problem in email. If you check the box to use Word as the editor in Outlook you end up sending very bad HTML full of gibberish that is not part of any official HTML standard known to the W3C. 

[quote]The Bat does a terriable job with HTML[/quote]

I didn't know that. But you can't blame it. It's not easy to do. Outlook Express uses Internet Explorer to do HTML parsing, and that's a full-blown browser, so naturally that's going to do a more polished job. However, the down side is that that's probably not a very safe thing to do--all that complexity and functionality brings security problems with it. (However, OE does, these days, at least use the "restricted" Internet Zone in IE by default; it used to run scripts and all sorts of nonsense, which is why malware used to go through it like a dose of salts.)

In Office 2007, Microsoft has, apparently, switched to using Office's HTML viewer (the one used for Word) instead of IE for Outlook. I don't know why they made the change, but it will make Outlook less capable at displaying HTML.

I have options set to display msgs as HTML by setting Tools/options/Display fancy version.  I move mail to folders using filters on the NEW MAIL folder. Some of the mail moved to these folders are plain text from Yahoogroups and  and when displayed, have the forum overlay test on top of the msg text which obscures the  plain text. How can I display specific folders as plain text and keep HTML msgs displayed as I have it now set to do.  IS this possible??  [:D]

Not a direct answer to the question, but you may find this thread of interest:

http://community.pmail.com/forums/thread/1732.aspx

In particular, see Peter Strömblad's post--the third one down--for a link to an update the HTML renderer.

I used Pegasus some years ago and decided to take a took at it again to see how it has progressed.  It is, indeed, an excellent email client but it appears to have the same issues as some others I have used.  Having used Outlook for a very long time, I have become aclimated to its functionality.  I am not saying it is the best client around, just that it works well for me.  Change is always good, and keeps things interesting in a mondane and repetivitve email world.  My needs are simple.  
I need a client to access each account, notify me with visual and audio when new mail arrives, be able to play a different sound for each mail client, filters to move the mail to specified folders, watch for spam, and allow me to bounce unwanted mail, and display HTML and plain text msgs and respond in the format of the received msg.  

So far, I have found only one client that does all this and much more.  The only thing is HTML seems to get it problems.  HTML must be a difficult thing to process in email clients. The Bat does a terriable job with HTML, Outlook does not have all the features I want, and so on. I have tried most all of them and keep going back to Outlook for stability and functionality.  Barca Pro comes close, but still has problems with HTML, you have to keep switching options to get the functionaly you want.

I suppose I will have to keep looking, and maybe someday a "all things to all people" email client will pop up.  

Thanks for the time and interest to respond, much appreciated
Goody