Today, we had a local event whose first session started at 2:00 pm EDT, and at 12:00 pm EDT, I sent a reminder email to the registrants, but due to the email delaiy problem today it wasn't delivered until 3:00 pm EDT - somewhat embarrasing. I could and will in the future send the email earlier, but I don't want to send it so early that people might forget as they get into their day.
So there should be a way to flag emails that must be delivered in a certain time-frame, so that they get prioritized to go out before others that aren't as time-sensitive or if they can't be sent in that time-frame, they shouldn't be sent at all and an alert email should be sent to the system administrator alertiing him to that fact.