How to configure an E-mail distribution service using Postfix + Courier IMAP with SQLite as the credentials storage endpoint


While I was doing the migration from Ubuntu 14 to Ubuntu 16, I came across the high resource demands required by the new version of MySQL. I’m running on a very basic VPS with to few RAM, and so MySQL (was running 5.7) crashed much frequently, so I decided to switch a MySQL fork, mariaDB, in this case. Tried first with the last stable version, 10.3, than I discovered that this version was still with more problems and running with even more problems with the very low RAM, so I downgraded to 10.1, but still the problems persisted. I ran the mysqltuner script to adjust the mariaDB configuration according to this “hardware” requirements. I changed the max_connections variable and lowered the value to 2 or 3. Still discovered that the entire VPS has crashed just because of this. Then I increased the value to 10 and Postfix started to complain with authentication errors since the e-mail credentials are stored in a MySQL schema. On that MySQL there are running other schemas, one for a wordpress site with very low bandwidth, and other wordpress site for a business, with much more load than the last wordpress. You know, wordpress does not support officialy other SQL engines than MySQL, which is bad, very bad, but I discovered a plugin that allows you to use SQLite as a WordPress backend. Very good for the wordpress instance with much less load (Truly speaking, it right this one that is storing this blog). So I decided, if now I can use SQLite as the backend for an WordPress site, why not use it also to store email service credentials. Very unfrequentely I change those credentials, so I move on studying how Postfix and Courier could use a simple SQLite database to store the email credentials and other stuff Postfix implements like transports, or e-mail forwardings.