Gmail to task
The email that is really a to-do should not have to become a copy-paste. Install the UnaTask button in Gmail, and every message gets a Create a task action. One click and it is in UnaTask, with the subject as the title, a link back to the thread, and a due date already picked out of the text.
Add the UnaTask button to Gmail and turn any email into a task in one click, with a link back to the thread and a due date read from the text.