When scheduling a new campaign, you can choose the start time only on even hours. When the emails arrive for example exactly at 8:00 AM, it's suspicious to a lot of people and they correctly assume that something is going on. I heard this as a feedback from some of our campaigns.

Better would be to be able to customize the start time, for example 8:12 AM. If the emails are sent in multiple batches, it would be nice to be able to schedule these more in depth as well.