Having trouble wrapping my head around sending notifications from linux box to us windows users. If I try to telnet to our public ip for our exchange server I get connection refused which is fine. If I try it by netbios name it works because I have told exchange to allow the linux box. My question is how can I set up postfix correctly so when it wants to send an email to person@publicdomain.com that it uses our internal network and not try to connect externally?

a.) Save date stamped copy of “main.cf” and “generic” in /etc/postfix.

b.) Modify original main.cf to contain line that has
relayhost = <your exchange relay hostname>
Insure all other relayhost lines are commented out.

Here we use the short name for our servers [set in /etc/sysconfig/network on RHEL]. You can skip remaining steps if you use FQDN names rather than short names.

c.) Modify the end of the main.cf file to have the following:
# Generic mapping due to short name rather than FQDN in /etc/sysconfig/network
# dd-Mmm-CCYY <your ID>
smtp_generic_maps = hash:/etc/postfix/generic

d.) Modify the original “generic” file to have the following at the end:
# Generic mapping due to use of short name rather than FQDN in /etc/network
# dd-Mmm-CCYY <your ID>
@<postfix server hostname.localdomain @<postfix server hostname>.<yourdomain>

e.) Run "postmap /etc/postfix/generic"

f.) Send test emails from servers and verify it comes showing FQDN to you.

Thanks, was editing the wrong file.