Like many people who went online in the early 90s, I managed my first email account with my University's default Mail User Agent, Pine. As I amassed an unmanageable inbox, Pine was ready with the great temptation: Take the messages you want to keep and save them in separate files.
Yielding to this great temptation is the beginning of the great madness, years of refining your system of organization, setting up directories, moving messages around, staring into space trying to remember whether the pie recipe is under food, family/aunt_sarah, or things_to_try, trying search systems and mboxgrep scripts, symlinking files that belong in two or more categories, finding years-old files with twenty messages and all the similar ones under some other name you thought up later.
Gmail was a revelation to many. It said, "Computers are good enough to do the work for you now. Just dump everything in a big box. When you want to find something, let the computer search for it."
For many, this is enough, and a welcome outsourcing relief. Others need to be able to read and compose messages while offline, want to work only with their own locally-stored mail collection, or have other reasons for wanting to do it themselves.
Sup (pronounced "'sup?") fills the gap, incorporating some of Gmail's best features into a console MUA. It presents a unified view of mail from multiple sources, with the capacity to poll mbox files, IMAP folders, POP accounts, and Maildir directories. Once the day's feast has been gathered, messages are grouped into threads by message-id references and, optionally, subject lines. Opening a thread, you can alternate between views of new messages and all messages, with indentation making it easy to follow the conversation. Headers and quoted lines are collapsed by default for quick reading.
Most actions can be performed on entire threads instead of individual messages, letting you quickly dispatch large chunks of your inbox. As in Gmail, threads can be starred or given any number of labels prior to archiving, pleasing all GTD practitioners.
In addition to recalling messages by their labels, you can make fast and flexible searches on your archive with the Ferret engine.
An addressbook is automatically created from the list of people you've contacted.
Also, note that Sup is, to some extent, more a small toolkit than a
single executable, and you can use the scripts in
add new sources and update existing ones based on what's happening. I
like this aspect of it, and my Sup wrapper script has developed to
perform several email-related tasks in addition to preparing sources for
Sup, running it, and cleaning up after it.
I've seen a marked improvement in the speed and ease with which I process my mail with Sup. I let the mail pile up, then Sup lets me dump it all in a single inbox and fly through it with thread-based commands. It's not as customizable as Mutt, but that's been an advantage. I find the defaults reasonable and don't spend time tweaking a hundred settings.
I believe it's on track to remain my next step in email handling. If the Gmail approach appeals to you, it may be yours as well.