Server with 3 NICs - how to bind mailsending IP to one of my 2 WAN NICs?

marksemailproblem

I am running mailcow-dockerized on a server with 3 network cards, 1 is the lan interface, and 2 are WAN interfaces and I am hosting a separate domain on each of the 2 WAN interfaces. I am using Nginx proxy manager to reverse proxy mailcow services from my lan interface to one of my wan IPs - and when I set this up I set mailcow to use the correct IP for sending and receiving emails and it worked fine, but it seems on rebooting the server, the mailcow-dockerized server switches to use the other or ‘wrong’ WAN ip - how can I set mailcow-dockerized (or docker) to always use the correct WAN interface/address.

Any help or pointers will me much appreciated - thank you!

esackbauer

https://docs.mailcow.email/post_installation/firststeps-ip_bindings/

marksemailproblem

Thank you sir, here are my bindings settings
as you can see I am binding the mailcow services to my local lan IP and then I am using nginx proxy manager to reverse proxy to the correct WAN Interface - so I am thinking this may be a proxy/docker issue rather than an an mailcow config issue…

Then again maybe I need to amend the below to include the WAN IP I wish to use?

e.g. SMTP_PORT=x.x.x.x:25
etc… ?

Do you think this may help?

Just to recap my server has a lan IP of 192.168.1.19 and I am running mailcow-dockerized on the lan IP and reverse proxing the front-end services to one of my WAN IPs (O have 2 but I want to restrict all the services for my hosted domain to run on 1 of the WAN IPs and have set this up correctly with my DNS provider)

I am confused and thinking that as mailcow-dockerized is bound to the plan IP although I am reverse proxing the front-end services to the correct WAN IP - my server may be selecting one of the WAN IPs (in this case the wrong WAN IP) as the default gateway that docker/mailcow is using to send emails…

Does this make sense - or do you have any ideas?

Many thanks for your reply and any help on this!

esackbauer

marksemailproblem
Depends on your nginx proxy manager configuration. Usually its only suitable for http(s) traffic, and not for SMTP…
NginxProxyManager/nginx-proxy-manager1110
Maybe this helps. Good luck.

marksemailproblem

Thank you, I am only reverse proxying ports 80 and 8080 from my lan IP to the WAN IP for the SOGo front end and using Nginx Proxy Manager to deal with SSL - so I am not reverse proxying any of the mailcow SMTP ports etc… this is what leads me to suspect that the issue is more to do with how docker is internally selecting a default gateway to use from the machines three interfaces rather than any mailcow settings….

I will continue to investigate and if I find a solution I will update this thread in case it is useful for anyone else in the future.

But if you have any ideas… feel free!

Cheers

caylakpenguen

hello.
nginx

listen 80;

change to

listen 12.34.56.78:80;

chers 🙂

marksemailproblem

Thanks but nginx proxy manager and the webmail front end are working fine - its just an issue with the IP mails are being sent from on my server with 3 network interfaces.

I havent yet been able to restart the server after setting the smtp ports etc to bind to the wan interfacr i need, altough i may also try binding the ports to the lan ip and reverse proxing them…

Cheers!