Why do you need to verify emails with something like Zerobounce?
If you're buying, gather, or scraping leads, you have no idea if they're still working by the time you get them into your cold email campaigns.
People retire, staff turnover is high, employees quit and companies close.
When you send emails to inboxes that don't work, they don't just bounce back, they "ding" you within the email sending world. Send too many bad emails, and you start to look like a spammer, or some other untrustworthy agent.
And that starts to hurt your deliverability. Your email campaigns won't get delivered, so they won't get opened and replied to, so your dream of doing sales via email will die.
So, to make your campaigns more efficient, use a tool like Zerobounce to remove the bad email addresses and focus only on sending out the ones that will make it to the right place.