Loading
Find out before the send, not from the bounce report.
Verification is the least glamorous part of this and the part that protects everything else. A list with a few percent invalid addresses damages the sending reputation of your whole domain, which then affects invoices and password resets, not just campaigns.
This is the same work we do by hand in client engagements — it is pattern P03 on our work page, and it is the most common reason a client's email results collapsed without an obvious cause.
Malformed addresses and domains with no mail exchanger are rejected without spending anything with a provider.
Where the receiving server permits it, confirm the mailbox exists without delivering a message.
Valid, invalid, catch-all, role account and disposable are five different answers. Collapsing them into a single score is what makes verification results untrustworthy.
A failed address is worth keeping so it is never re-purchased or re-verified next quarter.
ProvidersVerification providers differ sharply in how they treat catch-all and role accounts. Configuring two and comparing is often more useful than trusting one.
Every one of these is a genuine constraint of the underlying data, not a gap we intend to close later. Anyone claiming otherwise is guessing on your behalf.
Honest limits
The playground shows what this looks like as an agent tool call and as plain HTTP — including what a miss and a refusal return. Illustrative, not live.