Email configuration documentation.

docs/hosting/email.md

@@ -0,0 +1,32 @@
+# Email configuration
+
+farmOS needs to be able to send emails to users. This is used for password
+reset emails, notifications, etc.
+
+Depending on how you have farmOS deployed, there are a few ways to configure
+your server to allow farmOS to send emails.
+
+By default, farmOS will attempt to send emails via an SMTP server installed on
+the same system. If you have [Postfix](http://www.postfix.org) installed, email
+should work without any additional configuration, although they will most likely
+be filtered as spam. [This StackOverflow topic](https://stackoverflow.com/questions/371/how-do-you-make-sure-email-you-send-programmatically-is-not-automatically-marked)
+provides guidance for avoiding this.
+
+## Docker
+
+The [farmOS Docker images](/hosting/install#farmos-in-docker) do not include an
+SMTP server, so you will see this error message when farmOS tries to send an
+email:
+
+> Unable to send e-mail. Contact the site administrator if the problem persists.
+
+There are two potential solutions to this:
+
+1. Install and configure the [SMTP](https://drupal.org/project/smtp) module.
+   This is a contributed Drupal module that allows emails to be relayed through
+   a third-party SMTP server. This module is not included with farmOS, but can
+   be downloaded into `[farmOS-codebase]/web/sites/all/modules` and enabled in
+   `https://[farmOS-hostname]/admin/modules`.
+2. Create your own Docker image which inherits from the farmOS image. This
+   image can install an SMTP server like Postfix, which can be configured to
+   send email directly, or relay it through another SMTP server.

mkdocs.yml

@@ -28,6 +28,7 @@ nav:
     - Introduction: hosting/index.md
     - Installing: hosting/install.md
     - Updating: hosting/update.md
+    - Email: hosting/email.md
     - 1.x Migration: hosting/migration.md
 theme:
   name: material