connection refused to a domain on another virtual machine

Hi there.

First i want to explain the situation.I have 2 virtual machine.

• VM1: have 1 public IP pointing to 192.168.0.30
• VM2: have 1 public IP (diff from VM1) pointing to 192.168.0.34.

I can send emails to yahoo, gmail, etc, doesn't matter where, everything work, but if i want to send an email from a domain on VM1 to another domain on VM2 the connections is refused, cannot send it. This situation happen in both ways(VM1 to VM2 also VM2 to VM1).

I look in the mailog and i only got 1 msg "connection refused".

I don't know what to add or put so i can send emails from VM1 to VM2 and vice-versa.
Any ideas?
thanks in advanced

Forwarding on a standard router can only forward port 25, 465, 587 to 1 machine, and then has to be able to communicate back out via that same port.

rDNS has to be correctly setup as well as DMARC, DKIM, SPF and not to mentioned SSL or MTA-STS.

Pointing 1 public to a VM is good for test and learning.
But if you going to use these as a production server, they each need public IP's, not behind a NAT.

Using a NAT isn't going to get support from anyone really, since every router can be configured differently.

Thanks for your reply.

Basically i have an IaaS (Infrastructure as a Service) where i can make VM, VPN, etc.
IaaS managing for me DDOS, mirroring servers, back-up space, etc. (at a big lvl)

On that console i set the network adapter for in/out from public IP to private IP in any direction with any port, so not using the NAT ip from CentOS WebPanel.

rDNS is set for the main domain and IP of the server.

I also set Dmark, SPF, DKIM, based on the several online tools, my email server is set correctly.

I can send emails for any other domains that are outside my VM (gmail, yahoo, ymail, etc) and everything is working like a charm.

I ran into a similar problem when i try to curl from VM1 to VM2, i added in /etc/hosts the domain with the local ip and curl work perfectly. I'm wondering if i have to do something similar.

Also 25, 465, 587 are open both direction, do i need to add in some conf file the same option like i did in /etc/hosts?

Check the mail logs to identify where your VM tries to connect to when you send emails from VM1 to VM2. Make sure the MX records of the recipient's domain directs emails to the correct host.

What does happen when you run

Code: [Select]

telnet MX.HOST.COM 25
traceroute MX.HOST.COM
(MX.HOST.COM - mx record of the destination mail domain)

on the source mail host ?

Hey.
Sorry to reply after all this long time.

So first i telnet & traceroute to the domain (not the mx record) both gave me answer and it's correct, since i add in

Code: [Select]

/etc/hosts the domains with internal ip (192.168...), i need to curl data from 1 server to another.

Then i try to telnet & traceroute to the mx record (mail is the record for MX) and nothing, no answer.
I add on both server on /etc/hosts  192.168.0.x mail.domain.com and both telnet & traceroute give me answer.

When i try to send an email from 1 server to another, in mail queue, nothing, still refusing my email.


I notice that the port 25 is open only on TCP and not on UDP...

It looks like the problem is caused by misconfiguration (invalid A,MX,CNAME records) of the DNS zones of the domains and/or by DNS resolvers on your VMs.

So my recommendation is to check the DNS zones and resolvers on both VMs.

Looks like you need to check your configuration in your NAT on your router to your internal IPs.

Again, ports can only be forwarded to 1 internal IP, not multiple.
And even then things get tricky, because unless you can set your rDNS correctly, SSL, etc. won't work like they should.

It looks like the problem is caused by misconfiguration (invalid A,MX,CNAME records) of the DNS zones of the domains and/or by DNS resolvers on your VMs.

So my recommendation is to check the DNS zones and resolvers on both VMs.

thanks for the reply.
On both vm everything is ok, rDNS, CNAME, etc... double check those info.
Maybe i need to add smt more on dns manager.
this is my DNS record for MX

rDNS is correct, all my emails to Yahoo, gmail etc are delivered and everything is ok.

Looks like you need to check your configuration in your NAT on your router to your internal IPs.

Again, ports can only be forwarded to 1 internal IP, not multiple.
And even then things get tricky, because unless you can set your rDNS correctly, SSL, etc. won't work like they should.

all the other options are working correctly, webservsers, ssl, etc even emails to gmail, yahoo, or other domain.

I'm wonder if on postfix there is some options, idk to set other local ip to check, since when i try to curl from 1 vm to another i had to add those details in /etc/hosts ... or maybe i should add on /etc/hosts the public ip and the domain...

i ask a person that know some rules, and he said to me to check the IP that he send the emails (is internal or public)...

i'll keep search for a solution, but if u any of u got any idea what to do, or what to test i'm here for it