I would like to know how to do this as well for tasks that do not have due dates. I have been using chandlerproject.org for this feature which I live and die by but want to switch to rtm for the additional features it supports. How does one get daily email reminders for ALL active tasks?

The daily email includes all of the tasks due that day, but not overdue ones. This has been requested countless times.

As for daily reminders of all tasks, including undated ones, I do not know of a trick to make that happen.

The manual for this is here: http://www.rememberthemilk.com/help/answers/reminders/setreminders.rtm