Follow Up Reminder
Schedule a follow–up reminder that will notify you when there is no response to a particular email.
And add the ability to edit a reminder after the email is send. As it works now with airmail reminder you can not edit or remove a reminder meaning the reminder list just get larger and larger as you use this feature.
Simon Hemph commented
nice, but how do I clear and expired or change a reminder? I do not want to delete the mail as I the will lose the history with the emailed person.