Email waiting reply list

[anoc]

Is your feature request related to a problem? Please describe.
Working with email, let's say thunderbird or outlook is all good until you come up to the situation where you use it alot and send messages that you'll need answer for. Usually don't get answer for the 5% of mails and then forget it. Read recipies work wrong-way around. Adding labels makes just more work for oneself if i need to start to manage all the reply-got checkboxes myself

Describe the solution you'd like
When sending email, there is a box to tick, "need answer" and maybe a due date.
If the mail is answered, then the task is automatically marked off, but if not, I can view all mails that are awaiting answer
and mail app also alerts them when due date and no answer

Describe alternatives you've considered
Doing manually with labels or task-manager, that's too much of work because automation is missing

Additional context
Each email has id, that this plugin could scan that is answer received. It should skip mails that are "out of the office" auto replies or undelivered errors. This would be good for example in thunderbird or gmail addon