Re: What is the diff between "POP3", "IMAP" and "SMTP"?

From: Robert Heller (heller_at_deepsoft.com)
Date: 01/16/05 

Date: Sun, 16 Jan 2005 16:46:03 +0100

  santa19992000@yahoo.com,
  In a message on 16 Jan 2005 06:46:38 -0800, wrote :

s> What is the fifference between "POP3" and 'IMAP", which one is better?
s> and why?.

POP3 and IMAP are different Mail reader server protocols. POP3
generally operates on the principle of storing mail on the local
(client) machine and IMAP generally operates on the principle of storing
mail on the remote (server) machine. It is also possible to 'tunnel'
IMAP via SSL providing a secure, encrypted network interface. Because
IMAP only downloads header info, it is possible to access your mail from
multiple client machines with a consistent mail folder tree. POP3
downloads whole messages and normally deletes the messages from the
server's mail spool. The presumption is of a user with a *single*
client machine which is the sole point of mail reading. I don't believe
that it is possible to use SSL with POP3, thus POP3 is insecure.

s>
s> Also why SMTP is needed, can't do that function by either "POP3" and
s> "IMAP"?. thanks. Can all these three applications provided by single
s> Linux based computer?. If I need those three apps, while installing RH
s> Fedora, which one I have to select?

SMTP is the (anonymous) mail transport protocol. It is used for
*sending* mail, not receiving mail and is implemented by a MTA such as
Sendmail or QMail. POP3 and IMAP are account-based protocol for
*receiving* mail, never for sending mail. Think of the difference
between the mailbox at the end of your driveway and the Post Office
itself.

If you want to use a single Linux based computer as a mail *server*,
you need to install a MTA, which implements SMTP. Commonly Sendmail.
Plus you would need to install the POP3 and IMAP servers as well, so
the local users can access their E-Mail via network-based E-Mail
clients (eg Thunderbird, Eudora, etc.). It is certainly possible to
install a MTA (SMTP protocol) *and* the POP3/IMAP servers on the same
server. Commonly done at small to medium ISPs. *Larger* ISPs often use
separate machines for the MTA and the client/account servers for
security reasons.

For a *workstation or desktop (or laptop)* that you are using to
*access* E-mail on some *remote* server, you don't need anything other
than the Mail client software (eg. Mozilla, Thunderbird, etc.). The
client software speak the various protocols (SMTP for outbound mail,
POP3, IMAP, or SSLIMAP for inbound mail) with the remote server(s).
Linux distros *always* install a local MTA (eg sendmail) for local mail
(various system daemons need to be able to send local E-Mail to local
users, often root), but this does not necessarily have anything to do
with E-Mail on a remote server (unless you are have lots of fun with the
likes of FetchMail or some other advanced E-Mail fun and games).

s> (workstation/desktop/server/custom)?. Also I need apache server, to
s> maintain web server from home?.

No, unless you want to implement a 'mirror' of your web server on your
home box for local (private) testing purposes -- useful for CGI scripts,
etc. You might want to install the apache-docs package on your home
system, just to have a fast off-line access to them. Get a copy of the
Apache Bible!

Oh, specifying 'server' will likely install a MTA (eg. Sendmail) and the
package contain POP3 and IMAP/SSLIMAP (under RH POP3 and IMAP are in the
same RPM package -- you need openssl installed for SSLIMAP). If you
specific one of the client types, POP3 and IMAP won't be installed, but
a MTA (for local mail) will be installed. You should make sure that the
MTA is *properly* configured for your system.

s> If I need e-mail access, how do I have to register?.

This would depend on your ISP. Generally the various E-Mail clients
have some sort of 'setup wizard' for account configuration.

s>
s>

                                     \/
Robert Heller ||InterNet: heller@cs.umass.edu
http://vis-www.cs.umass.edu/~heller || heller@deepsoft.com
http://www.deepsoft.com /\FidoNet: 1:321/153

 

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