Using a list with certificate expiration dates, I would like to have an email sent to the owner of the certificate(who is external to my company), alerting them that they need to get a new certificate. I would like this email sent 15 days before the certificate expires. I've played around with the list and with workflow and I can't quite get it to work.
If the above is not possible, could I run something to send a link to each record in the list that is 15 days from expiring?
I am looking for recommendations. If any expressions/formulas are needed, I would need them as I can't seem to find the right one to work to kick anything off. I'm a new user if you can't tell already 
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