Sendmail - issue within DMZ for some servers but not all

UNIX for Beginners Q & A
1

Hi All,

I have a strange issue and I am not sure where the problem lies.

I have about six Ubuntu servers on our DMZ two of which were built on 18.04 from scratch the others were upgraded to 18.04 from 16.04.
The servers built from scratch can send emails from the server via sendmail fine, so the Firewall rules for coming from DMZ to our internal network is fine.
The servers upgraded to 18.04 cannot send out emails, it is as if sendmail does not work.

This is what I get

root@DMZ-Server:~# echo "test" | sendmail -v me@domain
domain: Name server timeout
me@domain... Transient parse error -- message queued for future delivery
me@domain... queued
root@DMZ-Server:~#

I have uninstalled & purged sendmail from a server that does not work and re-installed.
I have updated the sendmail.cf to point to the mail server

define(`SMART_HOST',`MailServer.domain')dnl

the Hosts file has the relevant info...

It still does not work...

could someone help or point me in the right direction?
I am having the same issue on all systems in the DMZ that have updated from 16.04 - 18.04

2

It's always a good practice to post the entries related to sendmail issues and errors found in the syslog files.

3

Just to make sure: you do have compiled the sendmail.cf afterwards, yes? Sendmail only uses the compiled form of its configuration file, not the cleartext file itself.

And, while you are at it: can you post the version of sendmail you use? I have no idea which one is included in Ubuntu...

I hope this helps.

bakunin

1 Like
4

Sorry I am out the office for a while..... so not in the office to check this out.

I done this:

/etc/init.d/sendmail stop
cp sendmail.mc hostname.mc
cp sendmail.cf sendmail.cf.25Mar2019
.... amended hostname.mc
m4 hostname.mc > hostname.cf
cp -p hostname.cf sendmail.cf
/etc/init.d/sendmail start

but I made 2 new servers from ubuntu 18.04 and they worked fine - send emails fine
but the ones that updated from 16.04 to 18.04 don't send... not sure if it is something to do with how networking is set up on 18.04 and 16.04 as the are different.
18.04 uses a yaml file and the 16.04 does not....

5

Forgot to say,

in our DMZ 2 servers built from scratch on ubuntu 18.04 - work
in our DMZ 2 servers updated to ubuntu 18.04 - do not work
in our DMZ 3 servers still at ubuntu 16.04 - do not work

All sendmail versions on DMZ and non-DMZ networks have the same sendmail version 8.15.2
version found by

sendmail -d0.1

this is why I am thinking it is something to do with the networking as they are different from 18.04 & 16.04