To schedule an email from Gmail, while you are composing an email you can set a customizable time to send the email by clicking the Schedule button.
Once hitting this Schedule button, a window will pop-up allowing you to choose a time to send your email.
If you choose to send it at a later time the button will update to the time selected.
After you schedule the email, it will appear in your Drafts folder in Gmail with the label Tout Scheduled Emails.
If you click into the draft, you are able to edit the content of the email, but be sure to click Schedule again, reselect your Scheduled time, and click Tout It!
You can always check on the scheduled email in your Scheduled folder in toutapp.com