Label to follow up on sent email
I would love the ability to apply labels to sent messages right from the compose screen. This would allow you to set up a folder like "follow-up" so that when you send an important email, you can remember that you're still waiting for a response.
And add the ability to edit a follow up/reminder after the email is send. As it works now with airmail follow up/reminder you can not edit or remove a follow up/reminder meaning the follow up/reminder list just get larger and larger as you use this feature. Also the ability to set a follow up/reminder as done.