i currently use tuta. it has a free tier, offers encryption, is open source, gdpr-compliant, and is 100% powered by green energy.

i have used mailbox in the past, which is paid (cheapest tier is ~€12/yr). i can recommend it as well.

i remember everyone sharing files (mostly movies) via usb in my IT class, in vocational school. a lot of people came to me because i had all the episodes of samurai jack (it wasnt remastered yet, so getting the full series was difficult). that was half a decade ago though, and i haven’t had a reason to do it since </3