Wondering from a legal and/or best practices standpoint: Let's say a person ("John Smith") subscribes (opts in) to one of our newsletters with the email address email@example.com. We also have the email address firstname.lastname@example.org on file for him (not due to subscribing, per se, but perhaps an old customer record). If email@example.com bounces later on, are we allowed (legally and/or ethically) to update his invalid email address in Marketo with firstname.lastname@example.org, the other one we have on file? Or would John Smith have to actively request/opt-in with email@example.com?
To further complicate the scenario, what if John Smith unsubscribed via a link on an email sent to firstname.lastname@example.org? In a country like the US where opt-in is not required, could we update his email address in Marketo to email@example.com since he has not yet unsubscribed for that email address? Or is that not ok since we know it's the same person? Are opt-ins and opt-outs tied to an individual person or to an individual email address? Does it depend on whether you're looking at this from a legal standpoint or an ethical/best practices standpoint?
I know in Marketo the unsubscribe is tied to the individual email address, and there is only one email address per lead. But we have many duplicates in terms of same person with more than one lead record, often with a different email address.