IMAP or POP3?
IMAP and POP3 are two ways of fetching email. The difference: with IMAP, mail stays on the server; with POP3, it is downloaded to one device.
With IMAP, mail and folders stay on the server. You see the same on every device and in webmail. This is what we recommend.
With POP3, mail is downloaded to this one device. Your folders then exist only on this device; other devices do not show them.
POP3 makes sense if you want to keep all mail locally or your mailbox quota is limited.