A "verified" email has been checked against the receiving mail server, and that server accepted mail for it at the time of the check. Catch-all domains accept mail for any address, so those are marked and treated as valid but unconfirmed.
The main set is far larger, about 270 million people, and includes business emails, personal emails, mobiles and direct dials where available. Those come from the underlying records rather than a live deliverability check, so they are best for reach and for phone-first outreach.
Buzz understands the difference. Say "verified work email" and it sticks to checked addresses; say "maximum reach" and it goes wide. Either way it tells you what it did and why.
Availability is never a delivery guarantee. Mailboxes change, and a good sequence still watches its bounces. More on verified contacts.
