Can't connect to mailcow containers through other containers on the same host

jonathanmmm

Hi,

I am using mailcow dockerized like given, only changing things in the mailcow.conf file.
I can’t connect via SMTP, HTTPS, or anything from any other container over my the public ip of my server. I can connect to another nginx from inside containers.

I tried SNAT_TO_SOURCE=my_public_ipv4_of_my_server

It didn’t help, I can access it from any other server or from the host, but not from inside other docker containers on the same host. I am using docker-compose for all other containers.

Hope somebody can help me, how to fix this.

diekuh

That’s called NAT reflection and a “problem”/misconfiguration in front of your mailcow, like your firewall. Not an issue with mailcow or Docker.

jonathanmmm

diekuh

Thank you, I completely forgot the firewall and that I only allowed connections form 80 and 443 from outside. But as docker punches holes into the firewall I was still able to connect to SMTP, and so on, but only thing that my firewall blocked was connecting these ports from other containers on the same host.