Available Protocols in Outlook

A protocol is a set of formal rules describing how to transmit data. There are protocols for mail, calendar, contacts, addressing, and secure communications. Table 2.2 lists the protocols available in Outlook 2003 and their properties.

Table 2.2. Available Protocols in Outlook 2003

Protocol	Description
Hypertext Markup Language (HTML)	A format for displaying information on the Web
iCalendar	A common format for exchanging calendaring and scheduling information across the Internet
Internet Mail Access Protocol 4 (IMAP4)	A format for sending and receiving Internet email messages from multiple folders
Lightweight Directory Access Protocol (LDAP)	A way to provide access to address and directory information over the Internet
Multipurpose Internet Mail Extensions (MIME)	A method of encoding attachments used by HTML email
Network News Transport Protocol (NNTP)	A protocol used to post and download newsgroup messages
Post Office Protocol 3 (POP3)	A protocol for sending and receiving Internet email (only supports Inbox)
Secure Multipurpose Internet Mail Extensions (S/MIME)	This protocol allows email messages to be digitally signed and encrypted
Simple Mail Transport Protocol (SMTP)	A popular protocol for sending and receiving Internet email
vCalendar	A format to send and receive calendar and scheduling information over the Internet
vCard	A format to send and receive information about people over the Internet

These protocols fall into several different categories. SMTP, POP, and IMAP are primarily used to send and receive messages. MAPI provides communication between mail-enabled applications. LDAP is an addressing protocol that allows clients to query data in a directory service over TCP/IP. MIME defines file formats used to exchange information across the Internet. S/MIME provides standards for digitally signed and encrypted communications. HTML, primarily known for its capability to render Web pages, is also used as a message transfer protocol for Web-based email services such as Hotmail. NNTP provides transfer of news messages between servers or between servers and clients. Finally, iCalendar, vCalendar, and vCard are standards that enable people to share calendar and contact information across the Internet regardless of messaging program protocols and formats.

Each of these protocols is covered in greater detail later in this book.