How to set up two seperate servers: SMTP and POP3 servers ?

[HaoDr]

Hi there,

I have just found out my ISP has two seperate mail severs : SMTP server at 203.162.5.1 and POP3 server at 203.162.5.2. So I just arise a question that how to set up SMTP server and POP3 server seperately in two Linux boxes. With such a configuration, how can POP3 server and SMTP point to the same mail box to send and receive mails ? Or we need set up a intermediate server to keep mail boxes ? I have been told about LDAP server, does it operate as intermadiate server to keep mail boxes for SMTP server and POP3 server ?

Moreover, please tell me mail servers (SMTP/POP3)operating mechanism, I have heard a lot about them such as mail forwarding functions, mail relay...If you know somewhere on Internet I can get information about this issue, please tell me.
Hao Dr

 

[marsd]

Several ways your mail hub can deliver mail this way:
there could be a relay between the two boxes; fetchmail
could be used from the pop box, or the traditional alias/
virtuser feature method could be used.

ldap can do multiple things for your mail, but it is not
a middle agent per-se..this is a large topic...

if you have specific problems go ahead and post them here and someone will try to help you.

 

[HaoDr]

Thanks . But I have vague idea of what you tell me, could you explain more details, or give me a sample configuration ? or if you know somwhere on Internet talking about this issue, please tell me.
Hao Dr

 

[marsd]

Two servers:
One mail hub, runs MTA(sendmail,postfix,etc..) masquerading for the domain and has the virtuser
option compiled into the configuration.

Another machine: internal or external to the public
network, has user acoounts that are aliased/virtuser
db's at the mail server.
The mail server can deliver mail to this machine (depending on the circumstances) if this machine
also runs a mail server, or hold this mail for fetchmail
to retrieve in a central account.
POP server retrieves or relays from the mail hub and then
the users get their mail.

######################
# INTERNET #
######################
^
|
(FIREWALL)
^
|
---------
* mail *
---------
|
#################################
# Private | Network #
# | #
# (POP MAIL SERVER) #
# / | \ #
# ' | ` #
# (user1) (user2) (user3) #
#################################

And any method of static nat and/or port redirection could be used in the above situation.
Mail can be complicated...you really need to know what you want to do and then plan towards it.