Ah! That solved my problem not seeing any .env configs. I was accessing it with fly ssh console -s -C "/app/bin/ciao remote" rather than just fly ssh console then remoting in.

Now I can see the Swoosh configs, Application.get_all_env(:ciao)

  {Ciao.Mailer,
   [
     adapter: Swoosh.Adapters.Sendgrid,
     api_key: "SECRET_SENDGRID_KEY_REDACTED"
   ]},

After that the problem became much more manageable (having access to Application .env is so helpful). The next issue I had was the api client, I thought with SendGrid I could set the :api_client to false, but apparently you need one.

config :swoosh, :api_client, Swoosh.ApiClient.Hackney

Did the tick! Thanks for all the help everyone!

@travisf, what does the following give you?

Application.get_all_env(:ciao)

If the result is [], I’d look at your mix.exs file and check the values returned from the project function, as that might not be setup as you expect.

Check if maybe the runtime.exs is somehow overriding the settings from config.exs?

That would be the best place to put the config so you don’t have to recompile the app to change the api_key, for instance.