I've been coding for over 20 years now! (WOAH, do I feel old)
I've touched just about every resource imaginable under the Sun (too bad they were bought out by Oracle)
Also, the assumption at the beginning about bounced emails isn't valid either. The server may send an unknown email address into a black hole (no bounce), whereas a valid known email address may bounce for reasons such as a full inbox or invalid contents of the mail being sent.
The closest thing you'll get is having the user click a link within the email. But also have the link in plain text as well in case the user agent strips out HTML.
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Word of advice, never regex for an email address. Check out this article with a list of crazy yet valid email addresses.
hackernoon.com/the-100-correct-way...
Also, the assumption at the beginning about bounced emails isn't valid either. The server may send an unknown email address into a black hole (no bounce), whereas a valid known email address may bounce for reasons such as a full inbox or invalid contents of the mail being sent.
The closest thing you'll get is having the user click a link within the email. But also have the link in plain text as well in case the user agent strips out HTML.