If you are going to use this function with Send Later, remember to set your reminder first before scheduling your email.
The menu proposes six time choices: in 1 hour, in 2 hours, tomorrow at 8 a.m., tomorrow at 3 p.m., in 2 days, or in 1 week. You will get a Reminder after this time elapses.
You can also set your own time.
As soon as you have done this, a note will appear at the bottom of your compose box, telling you when the reminder has been set for. Send your email.