I've had Rainlendar for a long time (bought in 2007), but one really annoying thing keeps me from using it more frequently than I would like. I can't figure out a way to have ToDo list in Rainlendar display all the same items as Outlook (Exchange mailbox) displays.
Rainlendar appears to only pick up the "Task" tasks, and not the email messages that are flagged for a response. Perhaps this is not possible, and only MS can aggregate items like this. But I would love to get an answer.
For instance, in the screenshot below, only the "Registration Confirmation..." task appears in Rainlendar's TODO list. The most common use case for me and my colleagues is to flag an email with an appropriate follow-up - this simplifies how users manage actionable items as they arrive.