Bugfixes

Bugs fixed in this release:

* Some multi-part posts were not displaying a page index to guests.
* Some digest emails were being blanked due to a mail processor bug.
* Automated mail merge is no longer waiting for the last email for a given user before dispatching the batch, so users will get important email like password resets independently of the pending generics like digest email and mention alerts.

FYI: Mail being returned from invalid email addresses will only be retried twice. After that, your user account is automatically locked. Don't forget to use a valid email address on your account!