On Mon, 2022-02-21 at 11:55 -0600, c. marlow wrote:
What format does Evolution use to store emails in?
Of the few folders mine does store locally, it's in maildir. I don't know if that's user-selectable, though. The preferences window even says it's maildir for the default "on this computer" folder, but that folder's not editable (there's only an enable/disable entire folder option for it).
I suspect though, that internally it sticks with maildir for storing any mail it's fetched itself. All the local mail folders I see in ~/.local/share/evolution/mail/ are maildir.
Maildir is a later improvement on MH (according to other authors), so I'll take their word on that and not debate it, but it's a similar scheme of individual files for each message, though without an index file.
You can create non-network accounts where it'll read mail files that are already on the drive (something else will have to bring them onto the computer), and then you have a choice of local delivery (no clues in the preferences interface as to what it reads), MH format, maildir format, standard Unix mbox spool directory, and standard Unix mbox spool file.
I seem to recall importing old mail spool files into Evolution, years ago, simply by dragging and dropping a spool file onto a mail folder inside Evolution's window, and it automatically handled parsing it. I'm fairly sure that was how I finally moved my old mailspool files from the old Dovecot mail server into the new Dovecot server using maildir. Every mail moving tool I'd looked at seemed to require a computing degree to understand how to drive it.
For my mail it accesses through my IMAP server, it doesn't appear to be caching them anywhere that I can see (and I've not asked it to).
Seeing how you mentioned satellite internet, that's one of the laggiest systems and you probably are best off pre-fetching all your mail as a batch, whatever protocol you use. Then you're just stepping through your local cache as you read them.