Post Office Protocol version 3
POP3 is an older email retrieval protocol that downloads messages from a mail server to a single device, usually deleting them from the server afterward. In its original form it sends usernames and passwords in plaintext on port 110, making credentials easy to sniff. Modern deployments require the TLS-protected variant on port 995, and many organizations disable legacy POP3 entirely because attackers use it to bypass MFA.