We've gotten some great responses from users that use Momentomail for exactly this kind of thing. One user also sends their "thanks for the great meeting" followup messages before their meetings even happen, and another send a series of emails at stages before the completion date of a project, "just a reminder, the paperwork for xyz project needs to be filed in 5 days", "...in 3 days", "...today", but she schedules these all months in advance.

Email is such a great scaffolding for all kinds of wonderful services, but because it's old, nobody seems to see it as the modern social app that it really is.