I'm not sure why this is a problem, really. E-mail is e-mail, and the great thing about it is that it's been e-mail for years and it will still be e-mail in many years' time.
Thunderbird is a decent native e-mail client. It does its job well enough already. IME, it's been stable and robust for a while now. Lightning is fine for basic calendar needs these days, too. Mozilla have hardly done anything significant to this whole area for a long time anyway, and short of some new protocol being developed or something like signed/encrypted mail becoming the norm, I don't see that the tools require a lot of ongoing development either.
I'd be far more interested in improvements to Firefox or, if we're talking about messaging, in having some kind of lightweight Exchange replacement with the same kind of ease-of-use so I don't have to configure a million text files on a Linux box to get a basic mail/calendar/contacts store set up. Personally, I trust the likes of Google (or any other data-driven/ad-funded freebie service) about as far as I can throw them, and they'll host my e-mail when they pry the keyboard from my cold, dead hands. :-)
Lightning is not really "fine" - it never properly worked for me properly. Integrating it with Exchange is a nightmare. It is sad that it was never brought to a level where you could confidently recommend it as Outlook replacement, and now it never will be.
Mail.app is way behind Thunderbird. On TB, I can do tags, I can do message flags, I can do search folders, I have 9000 ways of searching, I can add quick folders, I have great antispam engine... Mail.app is ok if you receive 1-2 emails per day and never need them afterwards. If you receive 300 and need to be able to find each of them years since, it is not even close to being adequate, let alone fantastic.
I have about 1 GB of personal email, going back to 2003, on an IMAP server. Mail.app searches this basically instantly—I get results well under a second. At work I have well under 100 MB of mail going back about 3 years, and Thunderbird won't give me the first result for about 10 seconds. The idea that Mail.app can't keep up with Thunderbird is absurd. I'd take Mail.app any day over Thunderbird.
I'm saddened by Mozilla's decision, because though I like mutt, I unfortunately live in the current decade and work with humans who are prone to sending HTML email, and Thunderbird has been the best Linux option for a while. I hope the KMail or Sylpheed people gain some development effort, because either one could be really good if it just had a few more developers.
>I unfortunately live in the current decade and work with humans who are prone to sending HTML email
More precisely, you work with humans who are unwilling or unable to configure their webmail accounts not to send HTML email because the webmail service providers make it hard to configure the accounts that way because that configuration reduces their ability to sell advertisements.
We have a company-provided mail setup so this isn't it at all. It's just the classic HR department liking lilac-colored Comic Sans for their email text problem.
The Mail.app searching now is so fast, it's bordering the incredible. It's made me rethink the way I archive e-mail. I really no longer need to sort everything into monthly folders in order to find things.
The 9000 ways of searching things in Thunderbird are not always an advantage, I found it makes it really hard for me to find things, because I have to select so many things. The searching of Mail.app makes me get what I want within 2 seconds for 95% of the cases.
If it doesn't there's usually a sensible drop-down suggestion of where to search (body, subject, recipient, sender). And if that does not help you, you can always use the system-wide Spotlight to drill down even further.
I've moved from Thunderbird to Mail.app about a year ago, and have been pleasantly surprised. I'm a pretty heavy mailer, receiving hundreds of mails a day and sending out 30-50. I also search my archives regularly and that has not been a problem.
I've not tried filtering into folders, but your mailserver should do that for you anyway.
I love Thunderbird. I use Thunderbird. I want Thunderbird to survive and be successful. But I've never actually been able to make full use of things like flags, smart folders, or the built-in anti-spam because it's all local to a single computer. Those benefits don't follow me to my phone, or to a friend's house, or between my laptop and desktop.
We either need more extensions to IMAP (but what clients would support them?) or we need better web apps.
Not being able to teach the server about spam is really a big shortcoming. I have it on my todo list for years now... Apparently there even exist standard protocols for that, perhaps there are already plugins for TB that can do that? And of course the server has to play along, too.
I went a bit off track, but I did want to make a relevant point: For my use case, the features you enumerated aren't competitive advantages because they're locked away in a single client on a single machine. Thus, for me, there are entire classes of features where native clients can't innovate, because I can't rely on those features being available in more than one place.
So from my perspective, Mail.app isn't "way behind" Thunderbird. Rather, they're at parity, and Thunderbird has a lot of other stuff that I can't use.
It won't help you with your phone, but isn't there a version of thunderbird on portableapps.com? These install and keep their data on a USB stick, so you can take it with you between desktop, laptop, work and friends' computers (no install needed).
Have you used Mail.app on OSX recently? It has most of those things. SmartFolders are the same as search folders I assume. There's a fast/robust search system with saved search queries. QuickFolders (the extension?) sounds kind of like the favorites you can add to the toolbar for specific folders/people/searches. You can flag messages in a few different ways plus color labels if you want to get fancy. Not suggesting you should switch or anything -- just defending an app I like a lot.
IMO it doesn't have most features of his list. It has ALL. And all of them implemented way better than TB. Searching E-Mails? Isn't TB still the application with two different convoluted interfaces for in-folder and all-folder search? Mail.app's search interface is absolutely brilliant in comparison. Even its Spamfilter is pretty decent, nothing like what OP described.
Yes, I was wrong about SmartFolders - this Mail.app has covered. No idea what you mean by favorites though - I don't see any such option, same for different labels. Maybe it's some new Lion version that added that?
Yeah I think that's new in Lion. The flagging feature is a little half baked since you can only pick from preset color labels. If there's a way of renaming them to something more descriptive I have no clue how to do it.
Mail.app has no problem searching and indexing all of my mail since 1998 (nearing 20 GB). I'm not sure what you are doing wrong... upgrade to an SSD maybe?
It doesn't though. OS X Mail uses Spotlight, meaning you can use Boolean operators and everything. It also has Smart Folders, for search queries you repeat often.
Thunderbird is a decent native e-mail client. It does its job well enough already. IME, it's been stable and robust for a while now. Lightning is fine for basic calendar needs these days, too. Mozilla have hardly done anything significant to this whole area for a long time anyway, and short of some new protocol being developed or something like signed/encrypted mail becoming the norm, I don't see that the tools require a lot of ongoing development either.
I'd be far more interested in improvements to Firefox or, if we're talking about messaging, in having some kind of lightweight Exchange replacement with the same kind of ease-of-use so I don't have to configure a million text files on a Linux box to get a basic mail/calendar/contacts store set up. Personally, I trust the likes of Google (or any other data-driven/ad-funded freebie service) about as far as I can throw them, and they'll host my e-mail when they pry the keyboard from my cold, dead hands. :-)