Add configuration examples

docs/content/advanced/mail-fetchmail.md

@@ -10,3 +10,26 @@ environment:
 ...
 ```
 
+Generate a file called `fetchmail.cf` and place it in the `config` folder.
+
+## Example IMAP configuration
+
+```
+poll imap.example.com with proto IMAP
+	user 'username' there with
+	password 'secret'
+	is 'user1@domain.tld'
+	here ssl
+```
+
+## Example POP3 configuration
+
+```
+poll pop3.example.com with proto POP3
+	user 'username' there with
+	password 'secret'
+	is 'user2@domain.tld'
+	here options keep ssl
+```
+
+By default the fetchmail service searches very 5 minutes for new mails on your external mail accounts.