[exim/fetchmail] A day in the life of an email

[Mark Phillips <mark@ist.flinders.edu.au>]

I am looking at setting up mail properly on my machine.  I have an email
account at university and use ppp to gain dial-up access to uni.  I wish
to set things up so that I can receive and send email from my local
machine (rather than rlogin to a uni machine to read email as I do at the
moment.)

Please excuse my ignorance, but I am a bit unsure about what I must do and
about exactly what happens with email.  Here is my current understanding
of what the story is:

1.  Email arrives at the mail server at uni with the address
"mark@ist.flinders.edu.au" and is stored in a spool directory there.

2.  I contact the mail server using fetchmail, asking it very nicely to
remove the email from my spool directory there, and send it to my machine
at home.  Fetchmail does this with the POP protocol.

3.  Fetchmail feeds this email into some black box (I don't understand
this bit - is it a file or is it a program that is sitting around waiting
for such events???).  Exim somehow notices that there is email coming into
this black box and stores this in /var/spool/exim/input.  Exim then looks
and sees that the domain of the message is "ist.flinders.edu.au". 
Fortunately this domain has been configured as the local domain in
exim.conf so exim knows to distribute these messages to local users.  It
then sees the user is "mark" and so knows to distribute this to "mark" on
the local machine.  It moves the email from /var/spool/exim/input to
/var/spool/mail/mark. 

4.  I then run a program such as "pine" which sees there is email in
/var/spool/mail/mark and enables me to read it.  I have received my email.

5.  I then decide to send a message to fred@banana.com.  I compose an
email in pine which puts the message in the "black box" talked about
above.  Exim again somehow notices it and stores it in
/var/spool/exim/input.  It sees that "banana.com" is not a local domain.
It decides to forward the email to some "smarthost" configured in
exim.conf.  What mechanism/protocol does it use to do this?  What should
the smarthost be?  Should it be my home machine (I think not??).  Should
it be the mail server at uni?  Anyway, somehow it passes the email on to
some machine that somehow knows what it is doing and delivers the email.

6.  I then send an email to "fred@ist.flinders.edu.au" who might be a
friend at uni.  Again exim gets this email, but sees that the domain is
"ist.flinders.edu.au".  I have configured this as a local domain so exim
trys to deliver this to a local user.  But fred is not a local user on my
home machine.  He is a user at uni.  I want this email forwarded on to the
machine at uni.  How is this done?


Well, I think this sums up the state of my knowledge or lack of knowledge.
I would appreciate any clarifying comments/explanations/hints etc.

Thanks,

Mark.



_/~~~~~~~~\___/~~~~~~\____________________________________________________
____/~~\_____/~~\__/~~\__________________________Mark_Phillips____________
____/~~\_____/~~\________________________________mark@ist.flinders.edu.au_
____/~~\HE___/~~\__/~~\APTAIN_____________________________________________
____/~~\______/~~~~~~\____________________________________________________
__________________________________________________________________________
        "They told me I was gullible ... and I believed them!"