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Chapter 11.
Pull Mail Protocols: POP and IMAP
E-mail is one of the most important network
functions in use today. Whether it's used to send a memo to a co-worker across
the hall or a correspondent across the globe, e-mail has come to be something
we rely upon on a daily basis. Linux includes extensive support for several
different e-mail protocols. This chapter covers one class of e-mail protocols
that are known as pull protocols, because the
mail recipient initiates the transfers. These protocols contrast with push protocols, in which the sender initiates the
transfer. (
Mail Protocol: SMTP, covers the most common push mail protocol.) Because e-mail
originates with a sender, push protocols are always involved in e-mail
delivery. E-mail transfers, though, typically involve several weigh stations.
Pull protocols come into the picture in the last stage of a transfer, or
occasionally at an intermediate stage.NOTE
align=left border=0> Although this chapter comes before
this book, you must have a working push mail server before a pull mail server
will be useful. Most Linux distributions install a working push mail server
by default, so you should have at least minimal functionality from the start.
If you're having problems with your push mail system, or if you need to
configure it in something other than the default way, you may need to skip
ahead to
then come back to this chapter.
This chapter begins with a discussion of pull
mail protocols, including when you should use one, and an overview of the two
pull protocols discussed in this chapter. The chapter then proceeds to a
discussion of how to configure Linux to serve both of these two protocols. This
chapter concludes with a look at Fetchmail, which functions as a pull mail
client that can then forward mail to other destinations using push mail
protocols.
