POP3

Download and Delete Model

POP3 (Post Office Protocol version 3) is an email retrieval protocol that downloads messages from a mail server to a local device, typically deleting them from the server afterward. This design dates to an era when users had a single computer and limited server storage. The protocol is intentionally simple: connect, authenticate, list messages, retrieve them, delete them, disconnect.

Limitations vs. IMAP

Because POP3 removes messages from the server, accessing your mailbox from a second device reveals an empty or incomplete inbox. Sent messages, drafts, and folder organization exist only locally on the device that created them. IMAPInternet Message Access Protocol. An email retrieval protocol that synchronizes messages between a server and multiple clients, keeping emails stored on the server. Supports folders, search, and partial message fetching., by contrast, keeps everything on the server and synchronizes state across all clients. POP3 has no concept of server-side folders, message flags, or push notifications. Despite these limitations, POP3 remains in use in environments where a single-device access pattern is intentional or where server storage is constrained.

Protocol Details

POP3 operates over TCPTransmission Control Protocol. A reliable, connection-oriented transport protocol that guarantees ordered, error-checked delivery of data through three-way handshakes, acknowledgments, and retransmission. The foundation of HTTP, SSH, and most internet services. port 110 for plain connections and port 995 for POP3 over SSL/TLSSecure Sockets Layer / Transport Layer Security. Cryptographic protocols that provide encrypted, authenticated communication over a network. SSL is deprecated; modern implementations use TLS 1.2 or TLS 1.3. (POP3S). The protocol is text-based: commands like USER, PASS, LIST, RETR, and DELE are human-readable. SMTPSimple Mail Transfer Protocol. The standard protocol for sending email between servers and from clients to servers (port 25/587). SMTP handles outbound delivery, while IMAP or POP3 handle retrieval. is the counterpart protocol for sending mail outbound. For any deployment that requires multi-device access or long-term server-side archival, IMAPInternet Message Access Protocol. An email retrieval protocol that synchronizes messages between a server and multiple clients, keeping emails stored on the server. Supports folders, search, and partial message fetching. is the recommended choice over POP3.