Internet Message Access Protocol (IMAP), originally called ‘Interactive Mail Access Protocol’, is a network protocol that provides a network filing system for e-mails. IMAP was designed in 1986 with the aim of making access to mailboxes and messages as they appeared to be on the local computer. Compared to POP3, IMAP offers more advanced functions such as managing messages on the server. A different protocol (e.g. SMTP) must be used to send mails. The Port number registered for IMAP with the IANA is 143. Port 993 is reserved for IMAP over SSL (encrypted connection, IMAPS).