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
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Thank you so much for your suggestion, we'll pass it along to the product team.