Thanks Mike for help.

1. DNS - noted

2. Installation -- inside our own premise on VMWare host.  Host with 2 LAN card, one for LAN and another for WAN.  WAN adapter had external IP independent from LAN.

3. Since new server not working on existing Domain name and IP, it is now running simulatenously together with current server but with different LAN and WAN IP for troubleshooting

4. Telnet -- already test within own LAN as well as externally (from my home and at another office) -- both can successfully telnet port 25 of new server, on both WAN IP (24 & 28 when trying to switch).

Existing server setup: Citadel on Ubuntu 18.04 VM on VMWare, WAN IP xxx.xxx.xxx.28.  Server had been running since 2018 and having maintenence issue therefore prepared to be replaced.

New server now prepared: Citadel on Debian 13 VM on VMWare, WAN IP xxx.xxx.xxx.24.  Completely new install and not migration.  Both server on SAME vmware host with same network adapter, both LAN and WAN.

Problem: after shutdown existing server, and replace the new server to IP ending with 28, it does not receive external mail nor passing MXTOOLBOX server test.  However when placing back to IP ending with 24, MXTOOLBOX test (using IP) works.  Returning the existing server back online will have everything working fine.

Tue Mar 31 2026 10:04:57 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Alan,

 

i think, i need some more details about your setup. 

The DNS entrys doenst need to change. 

Your Citadel installation is on premise / selfhosted inside your own network?

If the new server have a different IP Address, maybe it wouldnt work. Do you checked your Firewall ports and port routing ? 

If you Citadel is inside your network, can you telnet from a different computer to your Citadel Server ?

 

For more details about your setup you can mail me if you want. Maybe there  informations not for everyones eyes, but the solution is good for all. 

 

Greetings 

Mike

michael@g00r00.com

 

 

Forget to mention both Ubutnu and Debian had no Firewall enabled.  

External IPs also running without Firewall equipment/UTM until everything had solved.

Hi Alan,

first, happy easter to you and your family. 

Is there any MAC boundary to the old Maschine inside ESx ? 

If telnet works on internal lan and not from outside, so must be a routing fail from the firewall or antoher service. Also check for persisten custom routes. 

You also can do a traceroute from inside and from outside. Maybe this gives you some more informations. 

Greetings

Mike

Mi Apr 01 2026 02:09:39 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Thanks Mike for help.

1. DNS - noted

2. Installation -- inside our own premise on VMWare host.  Host with 2 LAN card, one for LAN and another for WAN.  WAN adapter had external IP independent from LAN.

3. Since new server not working on existing Domain name and IP, it is now running simulatenously together with current server but with different LAN and WAN IP for troubleshooting

4. Telnet -- already test within own LAN as well as externally (from my home and at another office) -- both can successfully telnet port 25 of new server, on both WAN IP (24 & 28 when trying to switch).

 

Existing server setup: Citadel on Ubuntu 18.04 VM on VMWare, WAN IP xxx.xxx.xxx.28.  Server had been running since 2018 and having maintenence issue therefore prepared to be replaced.

New server now prepared: Citadel on Debian 13 VM on VMWare, WAN IP xxx.xxx.xxx.24.  Completely new install and not migration.  Both server on SAME vmware host with same network adapter, both LAN and WAN.

 

Problem: after shutdown existing server, and replace the new server to IP ending with 28, it does not receive external mail nor passing MXTOOLBOX server test.  However when placing back to IP ending with 24, MXTOOLBOX test (using IP) works.  Returning the existing server back online will have everything working fine.

 

Tue Mar 31 2026 10:04:57 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Alan,

 

i think, i need some more details about your setup. 

The DNS entrys doenst need to change. 

Your Citadel installation is on premise / selfhosted inside your own network?

If the new server have a different IP Address, maybe it wouldnt work. Do you checked your Firewall ports and port routing ? 

If you Citadel is inside your network, can you telnet from a different computer to your Citadel Server ?

 

For more details about your setup you can mail me if you want. Maybe there  informations not for everyones eyes, but the solution is good for all. 

 

Greetings 

Mike

michael@g00r00.com

 

 

Hi Mike,

Happy Easter holiday to you too!

Because of holiday, the troubleshooting process had been paused and shall resume again.

The ESXi host had no mac binding arrangements -- I had other VMs running both adapters which can successfully use DHCP and static external IP separately

May try traceroute approach later.

Sun Apr 05 2026 07:26:39 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Alan,

first, happy easter to you and your family. 

Is there any MAC boundary to the old Maschine inside ESx ? 

If telnet works on internal lan and not from outside, so must be a routing fail from the firewall or antoher service. Also check for persisten custom routes. 

You also can do a traceroute from inside and from outside. Maybe this gives you some more informations. 

 

Greetings

Mike