Impliment Preview Retries

[jmbarne3]

Description
Develop logic that allows the mailer process to attempt to resend a preview if the previous attempt failed. With our current 15 minute send window, this would mean should the 1st attempt fail (say, at 8am for example), a second preview would then be sent at 8:15am. If that send should fail, a 3rd would be sent at 8:30am, and then a 4th at 8:45am, if necessary. On the 8:45am send - or in other words, if the live send time minus the current time is less than or equal to our send cycle - it would be communicated in the black bar that the email is not going to be send, and the email should be deactivated programmatically.

Why it's Important
This allows us to communicate issues via the black bar previews automatically, without someone necessarily needing to be on call to coordinate resends and deactivation.

Alternatives
We could just always have someone on call anytime an email is going out early in the morning.