Verification usually happens in stages: the domain must exist and accept mail, the mailbox must be confirmed by the server, and catch-all domains, which accept everything, are flagged separately because a mailbox cannot be confirmed there.
Bounces matter beyond the lost message. Mail providers watch bounce rates, and a campaign with too many will land the good addresses in spam too. Sequences built on verified addresses protect the rest of your outreach.
In Buzzlist, the deeper business profiles on Growth and Scale carry checked work emails, with catch-all domains marked. Other emails are real records that have not been checked. Which to use when.
