POP3 Client Commands

This is a list of the POP3 client commands. Useful for manually debugging POP3 mail connections.

Basic POP3 Commands (work in all implementations)

Commands in the AUTHORISATION state:

      USER name               
      PASS string
      QUIT

Commands in the TRANSACTION state:

      STAT                    
      LIST [msg]
      RETR msg
      DELE msg
      NOOP
      RSET

Commands in the UPDATE state:
```
      QUIT
```

Optional POP3 Commands (only work in some implementations)

Commands in the AUTHORISATION state:
```
      APOP name digest
```
Commands in the TRANSACTION state:
```
      TOP msg n 
      UIDL [msg]
```

POP3 Replies

      +OK
      -ERR

Other than the STAT, LIST, and UIDL commands, only "+OK" and "-ERR" are significant in the reply. Any text supplied in addition to the standard reply may be ignored by the client. However, if supplied, it may be interpreted by the client for extended functionality.