You could definitely do as mentioned above, but a broader approach would be to qualify the sources your scraping mails from. So you might try only .co.uk domains for example, that way if you get a lot of emails that are not .co.uk you know generally that they are probably good.Is it possible to use the scrape box email plugin to only get UK based email addresses? I've been searching youtube and the SB Forums but not finding the answer.
I've found a pretty good market at the moment and it heavily relies on email marketing.
Thanks