I need help configuring postfix mail server within AWS

Linux and Unix-Like Red Hat
1

I am trying to setup the postfix email server on Redhat Linux 6.5 running as an EC2 instance in AWS. I can do reverse port mapping to open a port
from our internal network to the AWS linux server, so we should be able to get to our mail server, even though it is a one way path from our internal
network to AWS. I just to figure out how to configure postfix to get to the open port for our network. This is from the /var/log/maillog file. I don't
know where it is getting the mail_smtp.domain.org or mail_smtp2.domain.org servers from. Could this be something that Amazon has configured?
Any help would be appreciated.

Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 1A865418A9: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 1957E418AA: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 17A38418AB: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 1BBF9418A8: from=<root@ip-10-10-10.101.ec2.internal>, size=493, nrcpt=1 (queue active)
Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 7FFDD418AC: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
Oct 10 16:05:01 ip-10-1-84-36 postfix/qmgr[23601]: 30B5E418A5: from=<root@ip-10-10-10.101.ec2.internal>, size=493, nrcpt=1 (queue active)
Oct 10 16:05:31 ip-10-1-84-36 postfix/smtp[25102]: connect to mail_smtp.domain.org[10.10.20.102]:25: Connection timed out
Oct 10 16:05:31 ip-10-1-84-36 postfix/smtp[25103]: connect to mail_smtp.domain.org[10.10.20.102]:25: Connection timed out
Oct 10 16:05:31 ip-10-1-84-36 postfix/smtp[25106]: connect to mail_smtp.domain.org[10.10.20.102]:25: Connection timed out
Oct 10 16:05:31 ip-10-1-84-36 postfix/smtp[25104]: connect to mail_smtp.domain.org[10.10.20.102]:25: Connection timed out
Oct 10 16:05:31 ip-10-1-84-36 postfix/smtp[25105]: connect to mail_smtp.domain.org[10.10.20.102]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25102]: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25105]: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25106]: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25103]: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25104]: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25102]: 1A865418A9: to=<myemail@domain.org>, relay=none, delay=3780, delays=3720/0.02/60/0, dsn=4.4.1, 
status=deferred (connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25105]: 1BBF9418A8: to=<myemail@domain.org>, relay=none, delay=3794, delays=3734/0.04/60/0, dsn=4.4.1, 
status=deferred (connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25106]: 7FFDD418AC: to=<myemail@domain.org>, relay=none, delay=3332, delays=3272/0.04/60/0, dsn=4.4.1, 
status=deferred (connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25104]: 17A38418AB: to=<myemail@domain.org>, relay=none, delay=3407, delays=3347/0.03/60/0, dsn=4.4.1, 
status=deferred (connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:06:01 ip-10-1-84-36 postfix/smtp[25103]: 1957E418AA: to=<myemail@domain.org>, relay=none, delay=3705, delays=3645/0.02/60/0, dsn=4.4.1,
 status=deferred (connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:06:01 ip-10-1-84-36 postfix/error[25164]: 30B5E418A5: to=<myemail@domain.org>, relay=none, delay=6311, delays=6251/60/0/0, dsn=4.4.1, 
status=deferred (delivery temporarily suspended: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:10:01 ip-10-1-84-36 postfix/qmgr[23601]: B5C6C40129: from=<oracle@ip-10-10-10.101.ec2.internal>, size=494, nrcpt=1 (queue active)
Oct 10 16:10:01 ip-10-1-84-36 postfix/qmgr[23601]: B8F1341884: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
Oct 10 16:10:01 ip-10-1-84-36 postfix/error[25266]: B5C6C40129: to=<myemail@domain.org>, relay=none, delay=23751, delays=23751/0.02/0/0.01, 
dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:10:01 ip-10-1-84-36 postfix/error[25267]: B8F1341884: to=<myemail@domain.org>, relay=none, delay=23715, delays=23715/0.02/0/0.01, 
dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to mail_smtp2.domain.org[10.10.20.103]:25: Connection timed out)
Oct 10 16:20:01 ip-10-1-84-36 postfix/qmgr[23601]: 4DB8A4189F: from=<oracle@ip-10-10-10.101.ec2.internal>, size=491, nrcpt=1 (queue active)
2

Two things to check:

1) Did you configure postfix to listen on the correct IP in /etc/postfix/main.cf? inet_interfaces is probably the option you are looking for. you can see if postfix is listening with:

lsof -i :25

2) are you allowing inbound port 25 traffic in your ec2 security group?

Setting up a mail server is not easy. If you are interested in a guide to get all the necessary pieces set up, here is what I used. This guide is based on ubuntu, but I was able to get all of this working on a CentOS7 KVM instance that I then converted and is running in EC2. The only real bang-your-head-against-the-wall pieces with these instructions were getting clamav and spamassassin and their associated milters to work properly. Once that is all working, converting it to use mysql for passwords and accounts was fairly simple.