Cannot connect SMTP between two Docker containers

Question

I have read:

How to get Docker containers to talk to each other while running on my local host?

I have two docker stacks running behind an nginx proxy.

discourse (trying to send mails).
mailu (full email stack, Listens on 0.0.0.0:587)

The mail server works perfectly for everything coming from and going to outside. Discourse works, with the one exception that emails cannot be sent via the smtp in mailu.

NETWORK ID          NAME                DRIVER              SCOPE  
2492bbae4093        bridge              bridge              local  
5eef88cc8484        host                host                local  
f8c0d60ec0a2        mailu_default       bridge              local  
7483f57ce6d3        none                null                local

From the host:

nc -v mydomain.de 587
Connection to mydomain.de 587 port [tcp/submission] succeeded!

Same from outside: connection succeeded

From inside the Discourse container:

mydomain.de [172.17.0.2] 587 (smtp) : Connection refused
mydomain.de [172.17.0.2] 12345 (?) : Connection refused (This is a non-existing port for cross-test)

I assume I have to create a shared connection between the containers, but could not get the syntax right.

Cannot connect SMTP between two Docker containers

0 Answers0