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Old 07-21-2003, 05:19 PM   #1
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Location: Budapest, Hungary
Distribution: SuSE 6.4-11.3, Dsl linux, FreeBSD 4.3-6.2, Mandrake 8.2, Redhat, UHU, Debian Etch
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Sender domain must exist?

We have a sendmail mailserver inside our LAN. It basically works, but I have the feeling that it is not configured quite correctly. However, I do not have a clue what causes the following faults:
- when the smtp server is specified as in the mail clients, then some mails sent by these clients are rejected by the recepients with 'Sender domain must exist' error. When the smtp server is specified as, no mails are rejected. However I must configure many clients to use; these are notebooks that may connect to the mailserver also from outside our LAN.
- some user complains that they cannot send mail to their own mailboxes from outside our LAN (they say they can send mail to any other addresses)
- I could not send a mail with pine from our mailserver either I specified or as the mailserver.
What can be the reason for the above faults?

And my final question: I want to enable the notebooks to send mail via our mailserver even when they are outside our LAN. However, these notebooks only have private IP addresses inside our LAN, and no public IP addresses when they are outside. Since they do not have static IP addresses, I do not know how to allow relaying for these machines only, and not for all machines on the internet.
What is the common solution for this?

Last edited by J_Szucs; 07-21-2003 at 05:21 PM.
Old 07-21-2003, 05:26 PM   #2
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Registered: Feb 2003
Location: Sparta, NC USA
Distribution: Ubuntu 10.04
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# Common e-mail tools
sendmail - postfix - sends mail to local users (and internet when configured correctly)
fetchmail - gets mail from internet accounts (non-Hotmail type)
procmail - sorts and delivers into separate mailboxes
mutt - mail client that sucks less than all the others
Email the Linux Way
Suresh Ramasubramanian's email guide
The Linux Mail User HOWTO
The Linux Electronic Mail Administrator HOWTO
SquirrelMail web mail
Why use Hotmail when there is LinuxMail?
Gotmail, a utility to download mail from Hotmail type accounts

A configuration file for sendmail that I found on Suresh Ramasubramanian's email guide:
dnl This is the macro config file used to generate
dnl file. If you modify this file you will have to regenerate 
dnl by running this macro config through the m4
dnl preprocessor:
dnl        m4 /home/phil/Documents/ > /etc/ <--Change to your path
dnl You will need to have the sendmail-cf RPM installed for this
dnl to work, if you use an rpm build of sendmail
dnl include(`../m4/cf.m4')
dnl If you compile sendmail from a tarball, use the include above.
dnl In this setup, you should create the file as cf/cf/ 
dnl (in the sendmail source tree: eg. /usr/src/sendmail-8.11.6/cf/cf
dnl Now give the command "sh Build".  Now copy the file
dnl as /etc/mail/ (please backup first!)
dnl If you are using the RPM build of sendmail, use the 
dnl include statement given below instead
define(`SMART_HOST', `') <--Change this
define(`confTO_CONNECT', `1m')
define(`confDELIVERY_MODE', `queued')
MASQUERADE_AS(`') <--Change this
FEATURE(`mailertable',`hash -o /etc/mail/mailertable')
FEATURE(`virtusertable',`hash -o /etc/mail/virtusertable')
dnl FEATURE(`relay_based_on_MX')
Old 07-21-2003, 05:30 PM   #3
Registered: Feb 2002
Location: Grenoble
Distribution: Debian
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You can make it work, but only if you give your mailserver public IP or forward all mail ports to it (smtp and pop3). It should also solve problems of users who can't send mail from outside and the notebook users (the public IP will work in both cases).

How is your DNS MX entry configured? Where does it point?
Old 07-21-2003, 06:23 PM   #4
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Original Poster
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We have one public IP for It is the IP address of our firewall, and port 25 of our internal mailserver is forwarded to port 25 on the firewall, so the mailserver listens there. Pop3 is OK.
However, relaying is only allowed for a remote premise of us. I can configure it, since that site has static IP address. The notebooks have no static IP addresses, so I do not know how to allow relaying for them.
Here are the MX records:
castor IN A
IN MX 10 mail IN MX 100 castor
;mail IN MX 13
Old 07-22-2003, 03:59 PM   #5
Registered: Feb 2002
Location: Grenoble
Distribution: Debian
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So it looks you need to configure your mailserver to use smtp authentication. Can't see any other way.
Old 09-10-2003, 11:38 PM   #6
Sticky Toejam
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Registered: Sep 2003
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There is another way. Google for "POP before SMTP" and DRAC. What happens is when a user "pops" his mail from your unix box the incoming IP address is added to a list similar to /etc/mail/access. This (incoming laptop IP address) will be good for 30 minutes (configurable) and then they'll need to pop again. The downside is that they have to pop to your unix box. If they don't have an account on it you will need to create one for them for just this purpose. For large networks DRAC is the better option.


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