As far as I can tell, there is no way to delay sending or set timing of email to go out. I would pay for the Yahoo mail if it had it.
In my gmail account (for work, no choice) I can delay sending of the email. I would really like to do this in Yahoo. I've checked the help feature and community and it does not seem to exist
Thank you so much for your suggestion, we'll pass it along to the product team.