Hi,

User harry could not reply to an email and was shown this message: 

You do not have permission to send Internet mail.

Please let me send email.

Cheers,

Harry

Dear team,

We had been running Citadel since 2008 and now preparing a new Citadel server to replace the old one because of the age and capacity.

We setup and configurared a new VM for Citadel, copied most of the running settings to it, and it works well internally, however it just not responsing to external messages.

That is, it successfully send messages, but not receiving any from outside.

Confirm all necessary ports are opened.

Running MX tool SMTP check on internet shows the server is not responding.

However if we telnet the server IP address, it responses.  

May I ask whether there are missing configuration we needed?

Alan Lau

Hi Alan,

Harry received an email from the internet but did not have permission to send a reply. Who can give me permission? What port numbes are is used for Citadel emails in and out?

Thanks for your help.

Harry

Dear team,

We had been running Citadel since 2008 and now preparing a new Citadel server to replace the old one because of the age and capacity.

We setup and configurared a new VM for Citadel, copied most of the running settings to it, and it works well internally, however it just not responsing to external messages.

That is, it successfully send messages, but not receiving any from outside.

Confirm all necessary ports are opened.

Running MX tool SMTP check on internet shows the server is not responding.

However if we telnet the server IP address, it responses.  

May I ask whether there are missing configuration we needed?

Alan Lau

Harry are you asking me about your question?

As long as you described, it looks like your account in Citadel was created with "Permission to send internet mail" option checked.

If you are not your Citadel administrator, you will need to found him to open that option for you.

Just my 2 cents

Alan

Tue Mar 17 2026 08:51:47 AM UTC from alanlau Subject: Re: Received not sent

Harry are you asking me about your question?

As long as you described, it looks like your account in Citadel was created with "Permission to send internet mail" option checked.

If you are not your Citadel administrator, you will need to found him to open that option for you.

Just my 2 cents

Alan

Sorry I mean "not checked" instead of "checked"

Thanks Alan for the help.

Harry

Tue Mar 17 2026 08:53:54 UTC from alanlau Subject: Re: Received not sent

 

Tue Mar 17 2026 08:51:47 AM UTC from alanlau Subject: Re: Received not sent

Harry are you asking me about your question?

As long as you described, it looks like your account in Citadel was created with "Permission to send internet mail" option checked.

If you are not your Citadel administrator, you will need to found him to open that option for you.

Just my 2 cents

Alan

Sorry I mean "not checked" instead of "checked"

Tue Mar 17 2026 08:51:47 AM UTC from alanlau Subject: Re: Received not sent

Harry are you asking me about your question?

As long as you described, it looks like your account in Citadel was created with "Permission to send internet mail" option checked.

If you are not your Citadel administrator, you will need to found him to open that option for you.

Just my 2 cents

Alan

Sorry I mean "not checked" instead of "checked"

Hi, 

you checked the DNS for a A Record and a AAAA Record ?

Some ISP will use AAAA only.

If you can telnet the port 25, it looks fine. Also you can check with mxtoolbox.

Greetings

Mike

Di Mär 17 2026 02:43:59 UTC von alanlau Betreff: New Citadel Installation not receiving mail nor response to external SMTP check

Dear team,

We had been running Citadel since 2008 and now preparing a new Citadel server to replace the old one because of the age and capacity.

We setup and configurared a new VM for Citadel, copied most of the running settings to it, and it works well internally, however it just not responsing to external messages.

That is, it successfully send messages, but not receiving any from outside.

Confirm all necessary ports are opened.

Running MX tool SMTP check on internet shows the server is not responding.

However if we telnet the server IP address, it responses.  

May I ask whether there are missing configuration we needed?

Alan Lau

 

Hi Mike,

I used to run the mentioned MX test by MXTOOLBOX and having the result of server not responding.

All DNS records were not changed as with the existing old Citadel server.  Everything works fine on old one, but just not the case if I directly replace a new Citadel with it.

I install and tested the new server on both Ubuntu 22.04 and 24.04, as I wonder it is the OS lead to not responding instead of Citadel.

Any idea on it?

Yeah,

i know the Problem. I got such problem with Ubuntu too. I think, the UFW is turned off. I fixed the incoming MTA and use Postfix -> rspamD -> SMTP Citadel 2025. For more compatibility, try a normal Debian installation for a Citadel only installation. 

Oherwise check what the logs say..

tail -f /var/log/syslog 

and trace it to a file to analyse whats going on. 

Mike

Mo Mär 23 2026 02:32:44 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Mike,

I used to run the mentioned MX test by MXTOOLBOX and having the result of server not responding.

All DNS records were not changed as with the existing old Citadel server.  Everything works fine on old one, but just not the case if I directly replace a new Citadel with it.

I install and tested the new server on both Ubuntu 22.04 and 24.04, as I wonder it is the OS lead to not responding instead of Citadel.

Any idea on it?

Thanks for suggestion, and it confirmed one of my suspicion: its the OS broke it instead of Citadel  ;>

Since I'm not too familier on Debian I may need some time to test this configuration and will come up again once I am able to test it.

Mon Mar 23 2026 08:10:30 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Yeah,

i know the Problem. I got such problem with Ubuntu too. I think, the UFW is turned off. I fixed the incoming MTA and use Postfix -> rspamD -> SMTP Citadel 2025. For more compatibility, try a normal Debian installation for a Citadel only installation. 

Oherwise check what the logs say..

tail -f /var/log/syslog 

and trace it to a file to analyse whats going on. 

 

Mike

 

Mo Mär 23 2026 02:32:44 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Mike,

I used to run the mentioned MX test by MXTOOLBOX and having the result of server not responding.

All DNS records were not changed as with the existing old Citadel server.  Everything works fine on old one, but just not the case if I directly replace a new Citadel with it.

I install and tested the new server on both Ubuntu 22.04 and 24.04, as I wonder it is the OS lead to not responding instead of Citadel.

Any idea on it?

 

Hi, its not that different to Ubuntu. Its the same base. 

So i think you dont have any problems to use it. How you install citadel on Ubuntu ? As a Docker Container or nativ ? you need to chown right on Ubuntu. 

The problem is not the OS itself. 

But if you can telnet citdael on port 25, it might be not a OS problem. i think its a administrativ right problem for citadel or the service.

you checked the status for citadel service ?

systemctl status citadel.service

Greetings Mike

Di Mär 24 2026 01:22:45 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Thanks for suggestion, and it confirmed one of my suspicion: its the OS broke it instead of Citadel  ;>

Since I'm not too familier on Debian I may need some time to test this configuration and will come up again once I am able to test it.

 

Mon Mar 23 2026 08:10:30 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Yeah,

i know the Problem. I got such problem with Ubuntu too. I think, the UFW is turned off. I fixed the incoming MTA and use Postfix -> rspamD -> SMTP Citadel 2025. For more compatibility, try a normal Debian installation for a Citadel only installation. 

Oherwise check what the logs say..

tail -f /var/log/syslog 

and trace it to a file to analyse whats going on. 

 

Mike

 

Mo Mär 23 2026 02:32:44 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Mike,

I used to run the mentioned MX test by MXTOOLBOX and having the result of server not responding.

All DNS records were not changed as with the existing old Citadel server.  Everything works fine on old one, but just not the case if I directly replace a new Citadel with it.

I install and tested the new server on both Ubuntu 22.04 and 24.04, as I wonder it is the OS lead to not responding instead of Citadel.

Any idea on it?

 

 

Hi Mike,

Successfully tested on Debian 13 and works like a charm.

Therefore I concluded it MUST be ubuntu's problem, or at least its on OS setting I'm not awared of.

I had prepared a native Debian 13 and using native installation by Easyinstall script.

Tue Mar 24 2026 05:38:54 PM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi, its not that different to Ubuntu. Its the same base. 

So i think you dont have any problems to use it. How you install citadel on Ubuntu ? As a Docker Container or nativ ? you need to chown right on Ubuntu. 

The problem is not the OS itself. 

 

But if you can telnet citdael on port 25, it might be not a OS problem. i think its a administrativ right problem for citadel or the service.

you checked the status for citadel service ?

 

systemctl status citadel.service

 

Greetings Mike

 

D

Great ;)

Problem solved. But i will test it on a new Ubuntu installation and figure out, what the problem is. 

Hve a nice day

Greetings 

Mike

Mi Mär 25 2026 01:32:16 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Mike,

Successfully tested on Debian 13 and works like a charm.

Therefore I concluded it MUST be ubuntu's problem, or at least its on OS setting I'm not awared of.

I had prepared a native Debian 13 and using native installation by Easyinstall script.

Tue Mar 24 2026 05:38:54 PM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi, its not that different to Ubuntu. Its the same base. 

So i think you dont have any problems to use it. How you install citadel on Ubuntu ? As a Docker Container or nativ ? you need to chown right on Ubuntu. 

The problem is not the OS itself. 

 

But if you can telnet citdael on port 25, it might be not a OS problem. i think its a administrativ right problem for citadel or the service.

you checked the status for citadel service ?

 

systemctl status citadel.service

 

Greetings Mike

 

D

I just writing here to report that my previous new Debian installation for Citadel wasn't working as expected, with same result that unable to receive external message nor response to MXTOOLBOX server test.

When I first preparing it I used another IP for both internal and external network and it works fine.  However when I change back to my original email domain's IP address it just not responding.

Even though it's not responding to MXTOOLBOX server test, it does response to telnet port 25.  

I had no choice but put the old server back and everything fine again.  I am still investigating the reason....

Hi Alan,

please try to figure out, whats going on.

Check Services on Ports:

ss -tulpn

Also you can swtich port inside Citadel to antoher MTA Port and check, if you can Telnet it. Do you import Setting from an old Citadel installation ? 

I checked lates Debian and Ubuntu Version with Citadel and had no problems. 

My Settings:

Mo Mär 30 2026 01:25:28 UTC von alanlau Betreff: Re: New Citadel Installation not receiving mail nor response to external SMTP check

I just writing here to report that my previous new Debian installation for Citadel wasn't working as expected, with same result that unable to receive external message nor response to MXTOOLBOX server test.

When I first preparing it I used another IP for both internal and external network and it works fine.  However when I change back to my original email domain's IP address it just not responding.

Even though it's not responding to MXTOOLBOX server test, it does response to telnet port 25.  

I had no choice but put the old server back and everything fine again.  I am still investigating the reason....

Hi Mike,

My server is running on VMs.  Since my new server is not working last week, I had reinstate the old server VM back to use the original Domain and IP, and I had the new server VM continue running but use another IP.

If running on another IP, it response to MXTOOLBOX mail server test.

If put the new server back to my original IP, it doesn't.

Had used your command to check the common ports  (24/456/587 etc) are all listening by Citadel only.

Will it be any relations to DNS setting that binded to the original old server? Such as MAC address binding?  

Mon Mar 30 2026 06:37:27 AM UTC from Motobike Subject: Re: New Citadel Installation not receiving mail nor response to external SMTP check

Hi Alan,

please try to figure out, whats going on.

 

Check Services on Ports:

ss -tulpn

Also you can swtich port inside Citadel to antoher MTA Port and check, if you can Telnet it. Do you import Setting from an old Citadel installation ? 

I checked lates Debian and Ubuntu Version with Citadel and had no problems. 

 

Sorry the previous message typo - ports 25/465/587