Bad schedule request email never sends or clears

[k7hpn]

If a bad email address (e.g. broken.@yahoo.com) is queued for an email job to be sent to them it does not send and never clears, the job runner just keeps trying.

Steps to reproduce

1. Put in a schedule request with a bad email address (e.g. broken.@yahoo.com).
2. Trigger an email (close the schedule request successfully in Ops with email configured).
3. Watch the logs (Error sending email setup x to broken.@yahoo.com: Invalid local-part at offset 0).

Expected behavior

Invalid email messages like this should be placed into a queue for an administrator to review. Administrators should be able to correct the address (in this case it's easy, remove the period at the end) or mark the email as "didn't send due to invalid email address." In the case of scheduled requests it should be noted in the scheduled request history.

Actual behavior

Error message repeatedly in the log.