Earlier quoted context omitted.
I read mail first on my phone with K9 (the old UI) a few times per day and accept invitations there to put them on my phone, which is always with me. Then I download mail with Thunderbird a few times per week. I use my domain providers POP3 servers. Yes, they bundle a mailbox with each domain. It's also IMAP and webmail but POP3 is better for my use case.
> It's also IMAP and webmail but POP3 is better for my use case. I'm curious as to why, if you don't mind! Are you specifically looking for "download only once then get rid of it"?
My mail stays on my computer, backed up locally and encrypted to a remote location.
I lose the ability to access old messages from remote but it never was a problem in almost 17 years of self employment. Before that, I already had about 13 years of downloaded emails, from the times when web mail was not a thing. No need to upload my old messages to Gmail, if this is even possible. I just kept using a local mail client. For my personal mail I remember some emacs clients, Netscape Mail (bundled with the browser,) Outlook Explorer then Thunderbird. I might forget something.