On Tue, Aug 17, 1999 at 09:43:30PM +0200, [EMAIL PROTECTED] wrote
> Ok let me get this straight:
> I use a total of three (four) apps to read my mail: (pppd(pon) connects to
> my ISP,) fetchmail gets the mail, passes it on to exim, which sends it to
> the (one and only) user: me, and I finally invoke for example "mail" to read
> and edit mail.
> "mail" is (basically) an editor.
> exim takes care of internal mail (inside my machine, between root and user
> or apps like cron)
> fetchmail handles the connection out-of-the-box (mailwise)
> pppd/pon does the actual connecting bit (dialing and passwording and stuff)
> Please correct a pitiful newbie if he be lead astray from the path of
> righteousness.
That's the way it works if you have a single machine (or small network)
with dial-up access to an ISP's mailbox.
Here's a more general description; please ignore it if it's confusing:
There are two kinds of programs that handle internet mail:
- Mail Transport Agents (MTAs)
- Mail User Agents (MUAs).
In the "traditional" UNIX world, MUAs are the programs that users
run to read or write mail. MTAs are the programs that MUAs rely
on to transport mail when you send a message so that it arrives
in the addressee's mail box.
MTAs usually receive messages either via SMTP on TCP/IP port 25,
or by having the MUA run sendmail; most PC mailers use SMTP, as
they can't assume that you have a copy of sendmail on your PC.
The MTA typically then transmits the mail message via SMTP to an MTA on
whatever machine handles mail for the addressee, and that MTA appends the
message to the user's system mailbox (usually /var/spool/mail/<user>).
Once it's in the mailbox, it's out of the hands of the MTA. If you're a
local user, your mail reader displays (and deletes, etc.) messages directly
from your system mailbox; some mailers transfer the contents holus-bolus to
some other mailbox in /home/user/mail or /home/user/Mail, some operate on
them "in place" in the system mailbox.
If you have a dialup connection to an ISP, there is an extra step involved;
your mail is on your ISP's mail server, but you have to transfer it to your
own PC. One approach, the default for most PC workstations, is to use a mail
program that downloads the mail using POP or IMAP directly into your mailer
(XFMail, Netscape, Eudora, etc. do this); this is convenient, but ties you
closely to a single mail program. The other approach, which Fetchmail
takes, is to download the mail using POP like a "regular" PC mail reader but
then to re-inject it into the local MTA (with appropriate adjustments to the
recipient addresses), so that it ends up in /var/spool/mail/<user> or
wherever you configure your MTA to send it. The fetchmail approach is more
flexible as you can use all the "regular" UNIX mail tools that you would
normally have available, rather than whatever is provided by your mailer.
In the context of this explanation, you are using:
Exim - Your local MTA
mutt, pine, whatever - Your MUA
Fetchmail - A bridge between MUA-land back into MTA-land
pppd, pon, etc. - Froth that you use to establish a network
connection required by fetchmail.
John P.
--
[EMAIL PROTECTED]
[EMAIL PROTECTED]
"Oh - I - you know - my job is to fear everything." - Bill Gates in Denmark
