Rated 5 out of 5 stars

Nostalgy is a must. Alternatives are not coming close. Quick Folder Move, for example, has no prediction, no keywords, no shortcuts, no string matching for account names, no was to limit to account, no meaningful sort, and no keyboard support for switching between folders.
I realize that maintaining it takes time and not being a paying customer puts me at no position to ask for its maintenance, so I would just recommend that the author establishes some crowd funding campaign that will allow us all to chip in.

Rated 1 out of 5 stars

This was the extension that made Thunderbird. Quick and streamlined message filing is a primary use-case that I would expect to come out of the box.
However, it doesn't, and Nostalgy seems to no longer be supported. I would thus recommend finding other e-mail alternatives...

I'm the original author of Nostalgy, and I have recently started using Quick Folder Move, which is enough for my own needs. You should try it out!