Apple Mac OS X Server Migration For Version 10.3 or Later Manuel d'utilisateur télécharger pdf (Page 11)

Chapter 1 Mail Service Setup 11

An advantage of using POP is that your server doesn’t need to store mail that users

have downloaded. Therefore, your server doesn’t need as much storage space as it

would using the IMAP protocol. However, because the mail is removed from the server,

if any client computers sustain hard disk damage and lose their mail files, there is no

way to recover these files without using data backups.

Another advantage of POP is that POP connections are transitory. Once the mail is

transferred, the connection is dropped and the load on both the network and the mail

server is removed.

POP is not the best choice for users who access mail from more than one computer,

such as a home computer, an office computer, and a laptop while on the road. When a

user fetches mail via POP, the mail is downloaded to the user’s computer and is usually

completely removed from the server. If the user logs in later from a different computer,

he or she won’t be able to see previously downloaded mail.

Internet Message Access Protocol (IMAP)

IMAP is the solution for people who need to use more than one computer to receive

mail. IMAP is a client-server mail protocol that allows users to access their mail from

anywhere on the Internet. Users can send and read mail with a number of IMAP-

compliant email clients.

With IMAP, a user’s mail is delivered to the server and stored in a remote mailbox on

the server; to users, mail appears as if it were on the local computer. A key difference

between IMAP and POP is that with IMAP the mail is not removed from the server until

the user deletes it.

The IMAP user’s computer can ask the server for message headers, ask for the bodies of

specified messages, or search for messages that meet certain criteria. These messages

are downloaded as the user opens them. IMAP connections are persistent and remain

open, maintaining load on the server and possibly the network as well.

User Interaction With Mail Service

Mail is delivered to its final recipient using a mail user agent (MUA). MUAs are usually

referred to as “email clients” or “email applications.” These email clients often run on

each user’s local computer. Each user’s email application must be configured to send

messages to the correct outgoing server and receive messages from the incoming

server. These configurations can affect your server’s processing load and available

storage space.

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Apple Mac OS X Server Migration For Version 10.3 or Later Manuel d'utilisateur Page 11