I would say that you should try balsa-2.2.0 (it is just out) if you can. It really tries to use the server-side of IMAP as much as possible (eg threading and searching/filtering is done via IMAP commands), and only loads the barely necessary infos to build the messages tree, and loads only the message you select on-the-fly.
Copyright © 2017, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds