docs: add config details for sending emails

crates/cli/README.md

@@ -118,11 +118,33 @@ The server should be able to notify the user when manual intervention is require
 
 ##### webhook
 
+Will send a POST request for some events.
+
 - **url** - the URL to POST the notification to and the
 - **secret** - the sync key used to sign the webhook payload
 
 See [Notifications](#notifications) for more details.
 
+##### email
+
+Will send an email for some events.
+
+- **from** - the email address to send the email from
+- **to** - the email address to send the email to
+
+With just `from` and `to` specified, `git-next` will attempt to send emails
+with `sendmail` if it is configured.
+
+Alternativly, you can use an SMTP relay.
+
+###### smtp
+
+Will send emails using an SMTP relay.
+
+- **hostname** - the SMTP relay server
+- **username** - the account to authenticate as
+- **password** - the password to authenticate with
+
 #### storage
 
 `git-next` will create a bare clone of each repo that you configure it to