Verifying B2B Client Lists That Are Mostly Catch-All Domains

A catch-all domain accepts mail for any address, so a verifier can tell you the domain is catch-all but not whether the person's mailbox exists. On B2B client lists, a large share of rows can land there. The agency answer is not to skip them or send them all, but to separate them, send in small batches, and report them honestly.

What you are dealing with

When a server accepts any address, a check for real.person@company.com and zzzz@company.com get the same answer. That is why these rows are marked risky, not valid. Background in what a catch-all domain is and catch-all emails: what to do.

It is not a flaw in the check. It is the limit of what can be known from outside.

Step 1: verify the whole list and export by type

Upload to the verify page under the client's workspace. Export valid, risky and invalid separately, then split the risky file into its types: catch-all, role addresses, could not check.

Step 2: treat each group differently

Group	Plan
Valid	First campaign
Catch-all	Separate campaign, small batches
Role addresses	Usually separate; they reach a group
Could not check	Retry first, then treat as catch-all
Invalid	Never send

Step 3: choose the likely mailboxes first

Within the catch-all group, rows with a name and a standard pattern (first.last) are likelier real than generic guesses. If the pattern came from the client's CRM, trust it more than one your tool guessed.

Step 4: send small, watch, then scale

Start with a small batch from a domain in good standing. Watch bounces for a day. If the bounce level stays low, send the next batch. If not, stop and review. The thinking behind it is in how many catch-all emails can you send and sending to catch-all emails.

Never send the whole catch-all file in one go from a client's main domain.

Step 5: tell the client what you did

Put the catch-all count and the batch plan in the report. Plain language works: "These addresses are on domains that accept all mail. We cannot confirm the person, so we send them in small batches and stop if bounces rise." The report template is in how agencies report verification to clients.

On the Agency plan, the branded client report carries this breakdown and can be shared as a PDF, CSV summary or link that expires in 7 or 30 days.

What to record

• Catch-all count and share of the list.
• Batch sizes and dates.
• Bounces after each batch.
• The decision to continue or stop.

What this approach cannot do

It cannot prove a catch-all mailbox exists. It limits the damage if one does not, and it shows the client that you handled the uncertainty on purpose.

Next step

If catch-all-heavy lists are most of your work, see the Agency plan for volume, workspaces and reports, or compare on pricing.