The email protocol that typically downloads messages and deletes them from the server is POP3.
POP3, short for Post Office Protocol version 3, was designed for clients that connect briefly, retrieve mail to a local device, and then remove the server copies. That download-and-delete model suited early users with intermittent or dial-up Internet connections, allowing messages to be read offline.
POP3 does not require deletion after download. Most clients provide a “leave a copy on the server” setting, which lets messages remain available to another device. That option can lead to duplicate downloads or unmanaged server storage because POP3 has limited support for synchronizing message status across devices.
IMAP is the usual comparison. It keeps messages on the server and synchronizes folders, read states, and deletions across clients. SMTP, meanwhile, is used primarily to send or relay outgoing mail, while MIME describes message content and attachments rather than mailbox retrieval.