I'm sure a lot of us can identify with have email related to both support/follow-up questions, and creative work (be it development/ design/ writing.)
There are times of day when I have the energy and mood to work hard, but not necessarily get into "the zone" required for creative work.
My own email/ task list is aligning more and more with specific energy modes, and less and less with any particular project/ person.
I'm getting way more done this way, letting my "mode" rule the roost.