As for non-Google email, my work uses Exchange – and I can’t reach an secure port for that without firing up the work VPN, so usually I use the shockingly clunky webmail alternative anyway – so its not like I am losing out on any functionality. I have a .mac address which truth be told doesn’t get used that much – and Gmail can suck in pop-based email into it’s own accounts anyway. It can be used with an unlimited number of Gmail accounts.

If you are a Gmail user on a Mac, I’d definitely recommend having a look at Mailplane.  It’s a nice way to get the Gmail-native way of handling email (which generally I love)  onto the Mac. I think its needs some improvement, such as integration into Apple’s iCal, and perhaps, if possible, the abstraction of some of the Gmail interface elements (such as gmail’s list of labels) out into native interface widgets.

Thunderbird 2 doesn’t integrate with the Macintosh Address Book, so that rules it out straight away, had to go straight to Thunderbird 3 beta. I got the latest, beta 3, released in July.

After about 5 minutes with Thunderbird 3 beta I was telling it to go fsck itself. Here’s why:

1. Installing Thunderbird 3 – what’s with the “@googlemail.com’ for Gmail? I use ‘@gmail.com’ and always have and always will. That’s the option I want. Oh sweet lord, it will force me to use @googlemail.com – that’s a disaster right there. Can be edited later, however, I discover. But still.
2. Thunderbird 3  “integrates” with the Mac address book, which is to say it will pull addresses from it, but it does this through it’s own horrible, horrible, interface. Bad Mozilla! I want to use – at all times – the Apple ‘Calendar.app’ and ‘Address Book.app’, OK? Their user interfaces. Not yours.
3. I got some mail with pictures in it. I can view the pictures by selecting “view external content” button for this one email. If I select the “always view external content for xxxx” it wants to add the sender to the address book (it’s internal address book). No Mozilla, that’s not what I’m asking for. I just want the graphics for that newsletter I get sent to be shown without me pressing extra buttons every time I get this newsletter. I don’t want their address in my address book!
4. Arrrrgh! My eyes! Jesus it’s ugly. And clunky. It feels like Windows all over again. Good lord. I can’t find any way to change the list display fonts. It’s probably in there somewhere, I will admit, but I can’t find it.
5. Every single folder, I have to individually select “view by thread”, as far as I can tell.
6. Search is an entirely separate window/dialogue. I can’t search more than one account at once. “Search Subfolders” at the top level includes Spam folder. There doesn’t seem to be a way to add a criteria that “Message is not spam”.
7. The terrible search function is the only basis for “Smart Folders” that I can find so far, therefore it won’t work for what I need. In Mail.app, I use three smart folders:
   1. All unread mail in any account or sub-folder thereof
   2. All mail in the Inbox of any of my three “personal” accounts, that is, mail directly addressed to me personally.
   3. All mail in the Inbox of my work mail account.
8. On the plus side, it does have good support for keyboard commands. I’m an old mutt user (before that, elm) so I love keyboard commands in my mail program. Mail.app has rubbish support for this.
9. Also on the plus side, Thunderbird’s threading display is a little clearer. Mail.app just puts all messages in a thread under the one hierarchy, you don’t get any sense of what message is a reply to which.

OK  Apple Mail.app lost some sent mail  once in the middle of a godawful crash (but a crash nonetheless), and I’ve always hated its horrible keyboard support. However maybe I am willing to take those risks and annoyances if this is the alternative experience. I know that Mozilla is open source, and full of all that open sorcery goodness, but I live and die via my email program, right after my IDE, and I want a pretty nice experience with it. Thus, I’m now in a bind – use a program that just proved to me its data integrity is not 100%, or use a program that that just gives me a truly horrible user experience and wants to screw with my choice of Calendar and Address Book?

Mac email program suggestions in the comments if you like (and no, don’t suggest Entourage, it’s completely off the menu).

UPDATE: I should mention that, for me, the deal killers are points 2, 6, and 7.