Another extremely happy user of the following combination waves hi: • Mutt • OfflineIMAP (to be replaced with `mbsync`; OfflineIMAP is not being ported to Python 3, unfortunately) • Notmuch — for fast indexing, searching, and tagging e-mails • Postfix — Mail Transfer Agent; offline queuing. Overall, it's one of the most robust pieces of software; Postfix never failed even once on me in nearly six years.
mbsync is far superior in resource usage and speed compared to OfflineIMAP, python3 would not help with that. combined with fdm filtering/sorting/archiving the speed has been incredible.
My mentioning of Python 3 was not related to resource usage. It was in context of Python 2 being deprecated.