Very good point, thank you. So when someone has sent you a task that is not using Ivelope and you click "Mark task as Done", the first time the user will be shown a popup on how to handle this, if he wants Ivelope to send an email every time he sets a task as finished, or if he wants to send an email when all tasks in an email are finished or if he just wants the tasks for his own personal todolist. Having unique features will bring in more users I think.
Curious how you handle something like the task feature when the recipient is not an ivelope user.