updated timesheet and email documentation (#349)

var/docs/emails.md

@@ -23,3 +23,31 @@ and its [documentation](https://symfony.com/doc/current/bundles/FOSUserBundle/em
 
 - Password reset 
 - Account approval (only if activated, see [User docu](users.md))
+
+## Troubleshooting
+
+You can test your email configuration with the command `bin/console -vv swiftmailer:email:send`, which will ask you for all required fields:
+- `to`
+- `from`
+- `subject`
+- `body`
+
+The email will be sent using the transport from your configured `MAILER_URL`.
+
+### SMTP does not accept emails
+
+If you have the following error in your logfile:
+```
+app.ERROR: Exception occurred while flushing email queue: Expected response code 354 but got code "503", with message "503-All RCPT commands were rejected with this error: 503-R1: HELO should be a FQDN or address literal (See RFC 2821 4.1.1.1) 503 Valid RCPT command must precede DATA " [] []
+```
+you might suffer from a wrong configuration (read the documentation linked above) and try a full featured SMTP URL with a dedicated user account for authentication:  
+```
+MAILER_URL=smtp://kimai@example.compassword@mx.example.com:587?encryption=tls&auth_mode=plain
+```
+
+If that still doesn't help , try to set a `local_domain` in the file `config/packages/local.yaml`:
+```yaml
+swiftmailer:
+    local_domain: 'kimai.local' 
+```
+This `local_domain` will be used for the `HELO` command when SwiftMailer contacts your SMTP.