Changes since DRUPAL-5--2-0-ALPHA2:
- #375422 by recidive: Fixed mails are sent to multiple recipients.
- by sun: Added HTML mail preview when Mime Mail module is installed.
by sun: Simplified settings form (UX).
by smk-ka: Fixed improper RFC 822 formatted date (by Mime Mail).
by smk-ka: Fixed empty mail body with Mime Mail.
by smk-ka: Fixed inconsistent linefeeds with Mime Mail.
by smk-ka: Fixed phpmailer_debug_mail not always rerouting.