We've had drip email campaigns on and off for years. Presently, we didn't have one because the last campaign's content was woefully out of date and we turned it off.
Today, I authored 4 new emails to go out on days 3, 6, 8 and 12 of a new user's trial and I modified the day 25 email letting them know about the end of their trial approaching.
I'll probably write up a few more after I see how these are performing.
This time around, I'm using Mixpanel to send out those emails and it has a really nice feature where I can set an event as a goal and it'll tell me the percentage of people who receive the notification and then go on to do that event.