[wtf77]

That's fine for your own domain, but I usually download my emails via IMAP and don't leave anything on the remote server. Finally, do you really keep your emails? Emails are ephemeral, often just informative, and if there's anything important, I process it and delete the email. I may archive 'sentimental' emails, but I rarely search the archive as I mainly delete emails.

[cosmic_cheese]

I keep mail because there’s been things that only became important or useful long after the fact. You just never know.

They can also serve as a sort of snapshot of a certain point in time that’s very effective at jogging your memory. I’ve had occasions where old emails reminded me of things that happened that I’d nearly forgotten or conflated details about.

[jrm4]

Do you mean "on the server?" I don't -- and just the opposite here; the cost of keeping literally all of them is close enough to zero, I never delete any emails and use "read/unread." I just archive yearly.