You can schedule emails that you compose, reply to, or forward to others on the Gmail website. This is how it goes.
Select the arrow to the right of the Send button in the email box where you compose, reply to, or forward emails, and then click Schedule send.

Gmail's Schedule Send option was selected
A pop-up window will appear with a selection of dates and times, including Monday morning, Monday afternoon, and tomorrow morning. Choosing one of these will cause the email to be sent on that day and at that time.

Alternately, you can select the precise day and hour you desire. Pick the date & time option from the pop-up box.

Options for a gmail email's scheduled send
To choose a date, use the calendar or type it into the corresponding field in the top right. Put the time in the field after that. When you're done, click Schedule send.

Gmail offers the opportunity to schedule emails for a specific date and time.
Your email will be scheduled, and you'll notice a small notification in the lower left corner of your Gmail screen. If you decide to change your mind, you'll also see an Undo option.
https://gmailguide.io