Glossary · Protocols
POP3 is an older protocol that downloads email from the server to one device, typically removing it from the server afterwards.
POP3 (RFC 1939) was built for one computer that connects occasionally: download everything, then delete it from the server. It knows nothing about folders or read state, so it handles several devices badly. Secure connections use port 995.
For almost everyone, IMAP is the better choice today. POP3 survives mainly in older setups and in tools that pull mail from one account into another.
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