See this recent HN discussion on an email overview with a good IMAP explainer: https://explained-from-first-principles.com/email/#internet-message-access-proto

See this recent HN discussion on an email overview with a good IMAP explainer: https://explained-from-first-principles.com/email/#internet-message-access-protocol https://explained-from-first-principles.com/email/#internet-... https://news.ycombinator.com/item?id=34846606 https://news.ycombinator.com/item?id=34846606 Proton Mail Bridge (for use with something like a desktop Thunderbird on Linux setup) does require the paid tier of Proton, which isn't immediately clear. Unlike Google they're not making money of harvesting and selling personal data, so I don't really mind. addendum: The IMAP state diagram is a finite state machine, interestingly enough: https://www.researchgate.net/figure/Finite-state-machine-of-the-protocol-IMAP_fig6_220070255 https://www.researchgate.net/figure/Finite-state-machine-of-...