Reminder on mail

When can we have ‘Reminder on a mail’?

There is already such a feature.

Right-click on the message and choose Snooze.
Once the snooze time has elapsed the message will appear as a new message in your Inbox again at the top of the list. When you dismiss the snooze, it will return to its original position in the message list.

You can also create a task or meeting from the message, if you want it to appear in your calendar.