If you want to have your email offline, you must use an application built for that. Thunderbird has its shortcomings but it does actually do the job. Web user interfaces have their place (such as on phones, which make development harder), but there is no replacing the desktop email client.
Fair, though in this day and age I find being offline is quite a rare event, and when it happens (I’m driving in the middle of nowhere), I don’t need my emails.
I’ll give TB another try. Web apps always feel terrible.
It's not about being away from the internet (for me), it's about keeping my data on my own machine. I'm still trying to figure out how to delete everything from the server and still have my own copy. But that is kind of a niche requirement these days. It's better for everything to stay available on the server, usually.
