jets
Hi there. Here is my approach. I would run the extension logic for every page that user enters and would try to find the emails by checking the words/strings for containing @ sign in them. Now, since they can vary a bit for multiple reasons (spam is an example) users tend to write something like "something @ mail com " to trick the antispam scripts that detect emails. Now, since you want it to run on multiple websites, this approach would vary. What I suggest is to have a list of websites that we need to cover first (a priority list) and do the lesser priority websites.
What I am sure of is that there is no one recipe to rule them all because of reasons that email can be presented. For example, the email can be hidden on the user, and the way to show it is to click on some button, and then the email will be shown.
Now, I have to ask about that verification process. What do you mean by that? What would I need to do to get that email on the "verified" list?
Anyways, feel free to hit me up so we can talk more about this. I am very responsive. All the best