Verification for agencies running client lists
Agencies inherit lists. A client hands over a CSV from a platform nobody at the agency has logins for, says it is clean, and the first send goes out under the agency's sending domain and the agency's reputation.
That is the specific exposure. When an inherited list bounces, the damage lands on the infrastructure you share across every other client, and the conversation afterwards is about your competence rather than their data.
The first send on inherited data is the risky one
A list assembled over four years by three different marketing managers has dead addresses in proportion to its age. Roughly a quarter of a B2B list goes stale each year through job changes alone, and nobody deletes anything.
Mailchimp suspends accounts on high bounce rates, and the suspension applies to the account rather than the campaign. On a shared agency account that means every client's sending stops while you open a support ticket.
The number that protects you is not a clean-looking summary. It is the record that you checked before you sent, and what the check could and could not resolve.
How the work gets done
The order that matters for agencies, rather than a generic checklist.
Verify before onboarding completes
Run the list during onboarding, while the client is still expecting work to be happening. A bad result found then is a conversation about their data. Found after the first send, it is a conversation about your judgment.
Send the two numbers, not one
Tell the client what share of their list got a definitive verdict and what the verdicts were. A summary showing 62% valid and 19% unresolvable is more useful to them than a cleaned file with no explanation.
Segment the catch-alls rather than deleting them
Catch-all domains cannot be resolved to a mailbox by anyone. Put them in their own send, watch the bounce rate on that send alone, and you have real data about that client's list instead of a guess.
Re-check quarterly, not once
A list verified in January is measurably worse by June. Build the re-check into the retainer and it stops being an awkward extra invoice.
What verification will not do here
What it costs
Most agency work sits between the $25 tier for 10,000 and the $139 tier for 100,000. Credits never expire, so buying a larger pack for the year and drawing it down across clients costs less than a per-client purchase and does not strand a balance when an account leaves.
Every tier works the same way. Unknown results and duplicates are never billed, and credits do not expire.
Questions we get asked
Can I resell verification to clients?
Buy credits at the volume price and charge whatever your agreement says. There is no separate reseller tier to negotiate.
How do I verify lists for several clients on one account?
Name each batch after the client. The name comes back on the status call and in the webhook, so attribution stays straightforward at invoicing time.
What do I tell a client whose list is 40% catch-all?
That their contacts work at companies running accept-all mail servers, which is common in mid-market B2B, and that nobody can confirm those mailboxes. Then send to that segment separately and measure.
Does verification protect our sending domain?
It removes the addresses that would hard bounce, which is the biggest single input to the reputation damage. It cannot fix content filtering or a domain with no authentication set up.
Try it on your own list first
100 free checks a month, no card. Run a sample and read the unresolved count before you decide anything.