by Hi Everyone,
I know that I have been posting a lot of questions the
last couple of days; however, I am just trying to learn
as much as I can with Unix especially Linux for the
past 10 months. Coming from a Windows background,
I think Linux performs so much better than windows.
I've successfully setup a mail server for server for my
home network. I registered for a domain (hnl.com)
from Network Solutions and my ISP assigned me a
static IP address 199.0.216.125. I've asked my ISP
to host my domain name, namely:
www.hnl.com (199.0.216.125)
ftp.hnl.com (199.0.216.125)
mail.hnl.com (199.0.216.125)
I am running sendmail-8.11.2-14 on Redhat Linux 7.1
with kernel 2.4.9. Furthermore, I am running sendmail
on the same box as my Firewall (bad idea, I know).
The firewall has the following address:
outside: 199.0.216.125
inside: 172.16.1.254
My private network is 172.16.1.0/24 and users on
this network have email account on the Linux mail
server in order to send/receive mail on the Internet.
Oh by the way, users send/receive mail via Microsoft
Outlook/Outlook Express. As I've said before,
everything works; however, I don't want to be a
dummy. I would like to understand the fundamental
aspect of mail server.
Here are my questions:
1) How many components are there in the Mail
Server? Is it true that for users to send mail to
other users on the Internet, SMTP (port 25) must
be running on the mail server. Is it also true that
SMTP is used to transport mail between
mail server?
2) In order or users on my private network to
receive mail from other users on the Internet,
I have to install a package called imap
(imap-2000-9) on the same system that I install
sendmail. From what I understand, imap, provides
services such as POP3 and IMAP2 so that users
on my network can retrieve mail. What is the
associations between IMAP/POP and SMTP?
3) Is it possible for me to run SMTP and IMAP on
separate Linux machines? I would like to move
the mail server to another machine behind the
linux firewall. I am going to get another static
IP address from my ISP and I will use Network
Address Translation (NAT) to NATed the mail
server to the Internet. What service will I have
advertise to the Internet, SMTP or IMAP? If I run
IMAP and SMTP on different machines, how will
mail from the Internet know how to get to my
network? I am really confused about this part.
4) I think I understand what "mail-relay" means.
I even modify the /etc/mail/relay-domains file
to allow only users from my private network
to use smtp to send mail (prevent spamming).
Am I correct with the definition of "mail-relay"?
5) Go back to question 3, if I replace the machine
that runs IMAP with a Microsoft Exchange Server,
is the same thing still applied?
I know some of the questions might sound obvious
to some people, but I have trouble understand the
concept. I've been reading a lot of books from
O'reily on this topic but the more I read about it,
the more I am confused about it. Please help me.
Many thanks.
David