Email client passthrough on port 25

[Paul Hill]

Hi There

we have our gateway/internet router forwarding traffic on (external port 25) to port 26 on 192.168.1.50 which is our proxmox mail gateway device . It then sends the mail to our internal web hosting and mail server on port 25 at 192.168.1.85 .

Anyone sending mail on the lan can do so on port 25 , anyone outside of the LAN cannot , they can check their mail but cannot send on port 25 .

Does the Proxmox server not pass through connectivity to the mail server on 25 for all traffic ?

Do we have a config setting wrong on the proxmox server ?

Thanks

 

[tom]

If you want to allow email sending on the internal port via the Proxmox Mail Gateway, you have to add their IP/Networks on:

"Configuration/Mail Proxy/Networks"

 

[Paul Hill]

So just to clarify ( please for give my lack of knowledge of this ) , we have around 20 clients that have software that usually logs into our mail server under their mail domain that we hold that uses port 25 to email reports for backups and server health reports . Plus about 100 other external clients that we hold their mail domain that need external access .

Traditionally the router forwarded external traffic port 25 straight to the mail server on ip 192.168.1.85 , it now forwards it to proxmox on Ip 192.168.1.50

If I have an organization with 10 email clients that need to log into our mail server to send mail from it on port 25 what do I put in the CIDR box ?
IP might vary due to the use of mobile devices used to send mail . can I simply put a domain name in there ?

Thanks for your patience

 

[Paul Hill]

Any additional feedback ?

thanks

 

[dietmar]

Any additional feedback ?

The setup looks complex, so I suggest you simply test if you can implement everything you need.

 

[Paul Hill]

The system isn't that complex .

We have a router that forwards all of the following ports to a single IP on our network that is an ISP config3 server for website and email domains . Ports 25 , 110 , 465 and 587 .

We host our own domain at work so our computers access our email domain both externally (on the net using laptops and phones ) and also internally on the Lan directly .

If I send port 25 to the proxmox server it filters the mails and forwards them on to our server ( ip 192.168.1.85 )

If I then try to login to the email server on port 110 to check for emails it works because at this point in time connections to port 110 (pop3) is being forwarded directly to the email server . I can login and check them externally on port 110 for the same reason , I can login externally and send on port 465 and 587 because again they are connected directly to the mail server on those ports .

I cannot use an external device to send because the Proxmox server is blocking connectivity to port 25 on the mail server when a device tries to connect to the smtp on the server .

How do I unblock this so that the external devices can connect through port 25 to the mailserver to send email ?

hope that clears it up .

We didn't have this issue using untangle because the machine had 2 Nics , one for input of all traffic , one for output of all traffic to the internal network . Your software does not allow this type of pass-through from what I can see .

 

[Paul Hill]

So ....

no suggestions ?

Thanks

 

[ChFin]

How do I unblock this so that the external devices can connect through port 25 to the mailserver to send email ?

Port 25 is server <-> server communication
Port 587 is client -> server communication (submission port)
Port 465 is obsolete (never intented for SSL/TLS submission)

Why would you want to connect with a client ("external device") to port 25 to send email?

 

[Paul Hill]

Because there are certain apps , clients that we have on industrial equipment that email status reports to us as part of our service contract with them , they only support port 25 , just like they only support 9 pin serial ports for connectivity etc . Many industrial processes stick to traditional communication technologies .

A particular client will have us host their email domain , same client has this equipment that emails out the reports , same client has employees that need to connect to send and receive mail .

 

[ChFin]

Many industrial processes stick to traditional communication technologies .

Your devices must be old..., the submission port 587 is standard since 1998. I doubt that you cannot change the port. I would contact the producer and ask them about port 587.
Any chance to redirect the port 25 traffic of the devices (only) to port 587 via firewall? Or set up a local mailserver in your clients network that talks to the proxmox gateway. ( device <-> clients mailserver for devices <-> ... <-> pmg <-> mailserver )