Generate dynamic myhostname for each pod

[jonathon2nd]

To comply with ISP's request, and according to smtp best practices, I would like to have dynamic hostnames for my smtp servers.

Simply using the HOSTNAME env var is not helpful as by default is something like mail-0. Looked briefly into hacking it to be closer to what I want, but decided it was not worth it.

I have made an attempt at this, I know it is not the best. But it works and I bet if y'all like it you can do it better.

By setting the following in the values.

# if the following is true, config.prefix.myhostname should not be set
GenerateHostName:
  enabled: true
  domain: example.com
  prefix: smtp

The following hostname will be used by each pod, and they will be unique and be built off of the public IP of that host.
smtp-###-###-###-###.example.com

We have tested this out and it is fully working. Have it in use right now and monitoring.

I hope that this can be useful.

[bokysan]

Hello @jonathon2nd.

Thank you so much for this commit. After careful consideration, though, I've decided not to merge it. I understand your reasoning for making it.

However:

1. This is a pretty edge-case scenario, which would not benefit a lot of people.
2. It includes a lot of external dependencies (e.g. on curlimages/curl:latest and http://ipinfo.io).
3. It works with helm chart only, there's no way to use this with Docker-only installation.
4. It increases complexity of the code.
5. Same thing can be achieved 'manually' by simply mounting the following script into /docker-init.db/:

#!/usr/bin/env bash
# This should be placed under /docker-init.db/set_hostname.sh
IP=$(curl http://ipinfo.io/ip)
IP=$(echo "$IP" | tr '.' '-')
PREFIX="prefix" # Alternately, this could be provided from environment
DOMAIN="example.org" # Alternately, this could be provided from environment
postconf -e "myhostname=${PREFIX}-${IP}.${DOMAIN}"

Again, thank you so much for the commit either way -- I'm happy that the image serves its purposes!

[jonathon2nd]

Thanks for the feedback! I took it and simplified the setup.

Setup here with this correction, just in case anyone else would find this useful.