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Sendmail setup

Posted on 2000-02-21
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Last Modified: 2013-12-23
Hi, here we go :

I have a site with no DNS and the ISP's mailserver sitting behind a firewall.
Users have been connecting to the mailserver, but I would like to setup a Sendmail Unix mailhub, that would keep all local mail, and forward all other mail to the ISP's mailserver. Users can then check both pops while saving ISP bandwidth. i.e.

Domain : a.com
Mailhub(sendmail): 1.2.3.4
ISP Mailserver: 10.9.8.7

if user joe sends to al@a.com the mailhub at 1.2.3.4 will KEEP the message, while a message to b@hotmail.com will be passed on by the mailhub to the ISP's mailserver for delivery.

How should I set up the conf files ?
Give a complete answer please :)

Jo
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Question by:johand
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by:jlevie
ID: 2542976
Well, that can be done, but it's going to be something of a pain for your users. They'll have to use a client that supports multiple pop servers or have two instances of a single server client.

It would make more sense to me to have all of your clients talking only to your local mailserver and it being responsible for all deliveries. If you have a full time Internet connection, you could just forgo the ISP's mail server entirely and have the DNS records changed to point the MX record for the domain to your mailserver.

If the connection is a dialup, fetchmail & similar can be used to periodically retrieve all of the mail from the ISP into your local mail spool. The FAQ for sendmail (www.sendmail.org) has some good information about how to configure the local server so that it won't try to connect and do immediate delivery (you'd configure the local sendmail to use a SMARTHOST).
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by:samri
ID: 2550627
johand,
   As far as sending mail, it's quite clear.  But how do your user receive mail.  Is it from the local Unix mail server or from the ISP server (both via pop).

samri.
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by:alien_life_form
ID: 2554825
Greetings.

The comments about receiving (POP, etc.) are well taken.Also, I do not much like the idea of running sendmail
without DNS (which can be done, but how do you like addresses like alf@[192.168.212.3]?).

What I'd do is:
Users talk only to the internal mailhub.

The mailhub also runs a nameserver. primary for local.dom or somesuch - that' s where the internal entowrk lives.

sendmail runs in  delayed mode
(O DeliveryMode=d (?)), with masquerade on (so local.dom does not leak outside)  and  arrange to have the link brought up every time the queue is processed.

Configure fetchmail to get mail from tha main server on a per-user, or perhaps multidrop basis (but see the multidrop caveats in the docs). Use etrn.pl (from the sendmail distribution) to deliver the local queue more frequently (every 5 minutes, say).

Users talk POP3 with the mailhub.

This is assuming you can't get a domain name and a static IP - which would open more convenient venues.

Cheers,
 alf
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Accepted Solution

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AGB earned 250 total points
ID: 2555542
1. You can have own real domain name.

2. Your domain mane can be correct resolved to real IP address on DNS your ISP.

3. You can configure DNS server for your private network (with your real domain name and records for each user) and set it as forwarding DNS server (local DNS requests process local intranet DNS , all request about foreign hosts your DNS forward to DNS your ISP). On ISP's DNS can be correct set link between your real IP and your real domain.

4. Then you can install local sendmail and in sendmail.cf you place real name your domain.

5. Lock smtp daemon in inetd.conf and unlock pop3d or imapd daemons.

6. Create all needed user's accounts (mail accounts can be created automatically).

7. Configure mail client software on your user machines and go...

good idea: have two DNS (one external with one record with your real IP address and one internal (intranet) with local records). First DNS set as forward server for second DNS. In that case from outside your local DNS records not visible...
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