Send emails using generic SMTP
Currently the sending of emails is only supported using Gmail. But coko-server
provides easy functionality to send emails using standard SMTP, and we should support that. This is how it is configured in the .env and in custom-environment-variables.js
We can use https://ethereal.email/ for local development.
We should consider, before we remove gmail-specific support, whether gmail provides possible benefits in terms of whitelisting against spam filters etc and whether we can make an equivalent connection to gmail using normal SMTP. It may be that some customers wish to continue with the gmail service.