Understanding the Types of Mail Accounts

Outlook supports a variety of messaging protocols. A protocol is a method of transferring messages between the messaging server and the messaging client. In some cases, your ISP or messaging server might support more than one possible protocol. To choose the protocol that's right for you, make sure that you understand the various protocols and what they can do for you. If you're in an Exchange environment, your system administrator determines which protocols you can choose to access your mail server.

POP3

One of the most popular protocols is POP3 (Post Office Protocol Version 3). Strangely enough, you don't actually ever hear about Post Office Protocol Version 1 or 2, but they were both used at one time or another. The first RFC (request for comments) for Post Office Protocol was submitted in October 1984. The intent of POP was to provide a simple method for workstations to access mail from a mail server. POP has undergone two revisions since 1984 and is now at version 3.

The majority of ISPs use POP3 for mail server access. POP3 operates on TCP (Transmission Control Protocol) port 110. One of the advantages to POP3 is that you can download messages from the mail server and delete them from the mail server after downloading. The messages can then remain in Outlook's Personal Folders file after they've been deleted from the mail server. The major disadvantage to POP3 access is that you can access messages only in your Inbox. Any message transfer to other folders must happen on the local client rather than the server. This isn't a large problem for most ISPs because most support only the Inbox folder anyway. However, if you're choosing a method to access Exchange Server, POP3 allows you to access only your Inbox. POP3 is designed as primarily an offline protocol. You connect to your mailbox, download messages, and disconnect.

POP3 only allows you to retrieve mail from the messaging server. To send that mail, POP3 email servers use SMTP (Simple Mail Transport Protocol). SMTP operates on TCP port 25 and is the preferred method of sending messages over the Internet.

What Is TCP?

TCP (Transmission Control Protocol) is a set of rules that's used in conjunction with the Internet Protocol (another set of rules) to send data in the form of message units between computers over the Internet. Internet Protocol handles the delivery of the data and TCP takes care of tracking the individual units that a particular message is divided into (packets) for better routing. A port is a 16-bit integer appended to the transmission of the packet. There are different ports TCP can use to transmit data. For POP3, that port is 110. For IMAP4, that port is 143.

IMAP

The other popular standard for Internet messaging is IMAP4 (Internet Mail Access Protocol, Version 4). IMAP is similar to POP in that it also offers a standard protocol for message transfer, but it has some key differences as well. IMAP was developed at Stanford University in 1986. It hasn't grown in popularity as quickly as POP3, but its advantages mean that it will likely eventually surpass POP3 in popularity.

Unlike POP's offline protocol, IMAP is designed to work in a variety of connection states. You can configure it for offline use, but you can also use it in online and disconnected access modes. You can access messages on the server without downloading them to your local machine. You can view, reply to, forward, and delete messages directly on the server. This method of mail access is very helpful for users who access their mail from multiple locations. Because the messages remain on the server, users can access their messages multiple times from any number of locations. You also have access to your entire message store. If your ISP supports multiple folders, or you're accessing an Exchange server via IMAP, you have access to every mail folder on the mail server, rather than just the Inbox. IMAP4 supports commands to create, delete, and rename folders on the server. It also supports commands to move messages from folder to folder and preview the contents of messages prior to downloading.

TIP

Although IMAP4 supports multiple folders on the server, all of these folders must be used to store mail. You cannot use IMAP to access Calendar, Contacts, Tasks, Journal, and Notes folders. In addition, Outlook's special folders, Sent Items, Drafts, and Deleted Items, can't be controlled with an IMAP client.


Another advantage of IMAP is that you can work with message headers rather than the entire message. An IMAP message header typically contains the first 3KB of the message. When viewing the message header, you'll see the address information from the message (To, From, Subject), as well as the first line or two of the message. If you're using a cellular connection or a very slow dial-up connection, you can download only the headers of the messages and then decide whether you want to download the entire message. IMAP includes better attachment support because it treats the message and the attachment as two separate items. Even though you can tell a POP3 client to download only messages smaller than a fixed size, the POP3 client treats the message and its attachment as one item. With an IMAP client, you can download the message header and attachment name, and then choose whether to download the entire message, just the message body, or just the attachment.

There are security advantages as well. With POP3 access, it's possible for your password to be transmitted across a network in clear text. IMAP uses a challenge-response method to authenticate users and keep your password secure.

HTTP

Starting with Outlook 2002, HTTP (Hypertext Transfer Protocol) mail clients are also supported. Currently, the only supported HTTP clients are Hotmail and MSN, but it's possible that other HTTP clients will be supported in the future. Enabling support for other HTTP mail clients is really more of a server issue than an Outlook issue, so if other HTTP mail services offer HTTP access to their messages, Outlook will be able to handle it.

Exchange

It's estimated that almost half of the existing Outlook installations are used to access an Exchange Server. Outlook 2003 supports Exchange 5.5, Exchange 2000, and Exchange 2003.

Using Outlook as a client for Exchange provides the advanced features of Outlook, as well as the information-sharing and collaboration features of Exchange Server. This is probably the most powerful method of using Outlook. When connecting to an Exchange Server, you can choose to view your messages on the server or download them to a Personal Folders file. You can also choose to create an Offline Folders file to access your Exchange items when not connected to the server. Using an Exchange account gives you access to all mail folders, as well as Calendar, Contacts, Tasks, Journal, and Notes. You also have access to the special folders of Drafts, Sent Items, and Deleted Items.



Special Edition Using Microsoft Office Outlook 2003
Special Edition Using Microsoft Office Outlook 2003
ISBN: 0789729563
EAN: 2147483647
Year: 2003
Pages: 426

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