Personally, I use mu4e (part of the mu software) to read, organise, compose and send emails. It uses a text-based interface, and runs from within the GNU EMacs editor. Emails are stored locally in the Maildir format.
It is actively maintained and open source, and not controlled by a company
Apart from xapian and EMacs, chances are that you have the dependencies already installed
Mails can be composed in HTML format, but this may take a few extra tweaks. (I do not do this myself.)
Emails have to be stored in the Maildir format to be indexed using mu and viewed with mu4e
Neither POP nor IMAP are directly supported. To fetch or sync emails from/with an external server, external applications can be called, like mbsync (for IMAP), offlineimap (same), or fetchmail in unison with a locally running postfix MTA (for POP)
I am not sure if I can recommend this solution, as it can be a bit technical compared with other email clients. For me, it is entirely worth it, though.
Personally, I use mu4e (part of the mu software) to read, organise, compose and send emails. It uses a text-based interface, and runs from within the GNU EMacs editor. Emails are stored locally in the Maildir format.
I am not sure if I can recommend this solution, as it can be a bit technical compared with other email clients. For me, it is entirely worth it, though.