On my company mail account I have collected circa 10000 mails during the past 10 years, which is circa 80 mails a month - and that is a lot.
If you’re not following multiple high-volume mailing lists since a decade and archive every single e-mail I don’t think its normal to have 50000 mails in a mailbox.
My personal order:
Repositories > AUR > Making an own AUR package > Making an own package not in AUR > Flatpak > Using an alternative to that application > consider if I really need it > AppImage