My needs/constraints are:

• Not slow.
• Does not force me to wait each time I need to check for new messages (Thunderbird did this to me so I gave up on it).
• Automatically checks for new messages without blocking the UI for manipulating messages already in the Inbox.
• Doesn't mess up the formatting of emails when sending emails to users using the Outlook client, and vice versa for those using Microsoft Outlook and sending messages to this client.
• Receives updates just like Firefox (and restarting Firefox is not a problem for me).
• Receives Microsoft Calendar invites.
• Allows me to send Calendar invites using a similar interface as does Microsoft Calendar such that I can actually see when some other person is buzy.
• Can be compiled from source and is open-source.
• Offers a way for me to program plugins in something other than C and C++, hopefully some reasonably R5RS-compliant version of Scheme, even thought that is not a critical requirement.
• Allows editing in plaintext, html, and rich-text.

I think the answer is still "No, you can't have all of what you want", but this is just to check to see if the situation has changed at all from when I looked into this a couple of years ago. But if you have suggestions to get me some of the above, I'd be interested to know about it.

Thanks in advance!
bg

Sounds like evolution would be about as close to that as you can get. Although as far as I know the exchange 07 implementation is still sketchy at best. Let me know if it fits in your scheme

I like kmail (on KDE3.5.x)

The only box in your list that I don't know if it checks, is the bit about "Microsoft Calendar invites", and I don't even know what these are.

AFAIK you can still run kmail (AKA kontact - with calendering and everything-integrated) on the gnome desktop, but you'll just have to accept the installation of a lot of KDE libraries (and with big HDDs so cheap now, who cares?

Take a look at it, perhaps with a "live" KDE distro. Disconnect your internet before you set it up as you will want to make sure it is set to "Leave messages on server", before you first connect, or your emails will be in a mess (no longer on the server for your usual program to fetch).

I'd recommend you avoid KDE4, but some people seem to like it.

I use Thunderbird with the Lightning extension (to provide calendar functionality) to do all the things you list except:That's not to say Lightning can't do that, it just means I don't do it, so can't say one way or the other.

There's a couple of niggles which I found with Thunderbird, most notably the fact it doesn't automatically re-wrap messages (plain text only?). There is, inevitably, an extension which fixes this (AutoRewrap).

I tend to send all my messages in plain text, though Thunderbird's perfectly capable of either HTML or Plain Text. I don't think Rich Text is supported, but I'm perfectly happy to be corrected on that. My understanding, from limited Googling, is that Rich Text is a Microsoft construct, and is therefore unlikely to be well supported by most FOSS software.

I can't check my emails at whatever interval I choose (or force it manually) whilst still using the interface as per usual.

Hope this helps.

Thanks everyone. I've got a lot of things to try.

I'm wanting to steer clear of anything that mandates dependency upon more recent versions of either GNOME or KDE, so that leaves me with either Evolution or Thunderbird I think. The reason for this is that it needs to be able to be built on systems where I don't have root access, so all of the bits and dependent libraries have to be relatively easy to download in source form an build standalone relative to my $HOME directory.

bg