Now they highlight it as big deal in new release without mention volunteer author of this BASIC feature which should be in mail client FROM VERSION 0.0.1!
It is pity, that Google Mail is «good enough» and it killed development of good desktop e-mail clients.
Thunderbird is best what we have (Cross-platform), but still very bad, and after killing off XUL plugins cannot be easily modified.
They exists for 21 year and now announce manual folder sorting! There is no support for Sieve (3rd party plugin? Dead after removing XUL)! There is no way to store folder settings as IMAP properties, and if I have two installations (on laptop and desktop, for example) I need repeat same setting or folders again and again — including selection of identity per-folder (again, not native functionality but 3rd party plugin, thanks, it is alive now!). No true message templates (per-folder, per-action, per-identity), only lousy "signature", broken in-line quoting in plain text messages, etc, etc, etc.
And it is best what I can use cross-platform :-(
21 years of progress and now we are here.