[FEATURE] Enhance Email integration test to work with remote hosts

[lezzago]

Is your feature request related to a problem?
Current email integration test wont work with a remote host and only works with a localhost

What solution would you like?
Extend the functionality to let the SMTP server bee created on the remote host if possible

[lezzago]

To run email integration tests for Notifications, we need to create a SMTP server that the OpenSearch cluster can connect with. With the current solution, this would only be possible if the OpenSearch cluster the tests are running against are on the same hosts and additionally not in a docker container.

A new solution to setup the SMTP server is needed where a remote OpenSearch cluster or one in a docker container can still connect to it, so we can run email integration tests successfully.