They say design is like art with constraints. Even art can thrive under constraint. Constrained materials. Constrained space. Constrained time.
That last one is interesting. How can email benefit from constraint? What if you never sent an email longer than one paragraph? What if you could only answer 1 email each day? A more commonly-tried constraint: what if you limited your email time to 1 hour at the start and end of each day?