But doesn’t Mac OS X 10.4 (Tiger)’s Mail 2 let you do this type of dynamic search with Smart Folders too? Am I missing something?

Smart Folders should definitely allow that. I know I have that kind of multiple-flag thing going in one of mine.

The combination of Mail Act-On and Mail Tags (both here) can do this pretty well for Mail.app. (Mail Tags is the newer one; it allows for tagging messages with project keywords, deadlines for action, etc, all of which can be used in Act-On rules and are — I think — Spotlight-able.)

I guess depending on what you mean, this is partially do-able in Mail.app, as is.

What’s nice (and in my opinion much improved) about Thunderbird flags is that they are a) numerous (Mail/IMAP has one digital flag: a message is either flagged or it’s not flagged), b) semantic (they mean something—don’t just change the background color, etc.), c) keyboard-assignable (remember, we have multiples here, not just one CMD-SHIFT-L), d) customizable.

So theoretically (and I haven’t really thought about this that much), I could have an “URGENT Work-related” email and an “Answer Anytime” email live in the same “Email to respond to” mailbox. This keeps everything under my nose (not buried in a folder someplace); they’re functionally the same (they both require an email response) but their semantic flag status lets me filter to just what I need without changing views (or waiting for Smart Folders to churn).

Being able to blast through a screen of messages with just keyboard commands every hour or so is basically my Email Valhalla.

(I’ve actually developed something similar to this by combining Mail Tags and Mail Act-On that I’ll be writing up soon.)

Merlin, I’d be curious to hear what you say. I am happily using Mail Tags and Act-On to parse my Inbox when needed, sending all emails that require more than 30 seconds to “respond later” or “turn into task,” then I assign due dates by which I must reply, and I have created smart folders (as the Mail Tags folks have suggested, with some modifications), to keep track of what needs to be done by when. It’s not GTD, it just helps create a smaller cloud of information that I can deal with dynamically at a given point. (I try to avoid wanking, meta work, etc., but then again, I still make heavy use of my Apple Newton.)

What I wish and can’t seem to get is a keystroke to get me into mailboxes. Yes, I know cmd-4 is sent, cmd-3 drafts, etc. I want additional assignable keys for other mailboxes, like my “respond to later” or “turn into task” boxes and a few others. Is there any help with that?