I have all my email since circa 1996 right here in my ~/Mail directory, something like 60+K messages accessible through Claws Mail, which is probably the fastest around both to operate and to do searches with.
I've changed my mail accounts several times in the past but kept in subdirectories all the old mail, which got indexed automatically, so I can search both my current mail archives and the 20+ years old expired ones in a breeze.
Backing up is just a matter of copying recursively the ~/Mail (mail archive) and ~/.claws-mail (accounts, address book, filters etc.) directories somewhere.
The issue with making email inboxes available for searching becomes even trickier when encryption (PGP/SMIME) is involved. Does anybody have a viable solution online/offline for this scenario?
The only solution I can think of is that your index is stored encrypted, but it has the ability to read and decrypt all your encrypted mail, and store that internally the same as any other email.
I have all my email since circa 1996 right here in my ~/Mail directory, something like 60+K messages accessible through Claws Mail, which is probably the fastest around both to operate and to do searches with. I've changed my mail accounts several times in the past but kept in subdirectories all the old mail, which got indexed automatically, so I can search both my current mail archives and the 20+ years old expired ones in a breeze. Backing up is just a matter of copying recursively the ~/Mail (mail archive) and ~/.claws-mail (accounts, address book, filters etc.) directories somewhere.
https://www.claws-mail.org/index.php?section=general
https://www.claws-mail.org/win32/