EλMail, ElMail is a browser messenger which helps you to

• backup and synchronize your mail accounts (offlineIMAP), in maildir format as one file per message.
• tag and organize your mail and notes with notmuchmail database
• search your mail archive for words, persons, tags... (logical expressions).
• write notes and send mail with your mail accounts (msmtp)
• notmuch supports end-to-encryption (untested) with the https://github.com/gkappler/Notmuch.jl julia package.

EλMail is a browser based open source email client for your backup data on your own disk.

Notmuch.jl is a julia wrapper for notmuch mail indexer (that supports arbitrary tags and advanced search).

Notmuch mail indexes emails into a xapian database.

• maildir can be smoothly synchronized with an IMAP server by offlineimap

https://youtu.be/uwQs88XXOTk