Bouncer Alternative: Verify the Catch-All Emails Bouncer Marks as Unknown

If you have shopped around for an email verification tool, you have probably run a list through Bouncer. It is quick, it has a clean dashboard, it markets hard on GDPR compliance and EU data residency, and its toxicity check is genuinely useful for spotting spam traps. For a lot of teams it is a perfectly reasonable starting point.

But if you have ever exported a Bouncer result and stared at a column full of “unknown” verdicts, you already know where this is going. The addresses Bouncer cannot resolve tend to be the exact addresses you most need an answer on. This post breaks down where Bouncer stops, why it stops there, and how Scrubby handles the same addresses differently.

What Bouncer does well

Let us be fair before we get critical. Bouncer earns its place for several reasons:

• Speed. Bulk lists come back quickly, and the API is responsive enough for real-time signup checks.
• Syntax, domain, and MX checks. The deterministic layer of validation is solid. Bad syntax, dead domains, and missing mail servers get caught reliably.
• Toxicity and spam-trap signals. Bouncer flags known complainers and trap-like patterns, which helps protect your sender reputation.
• Compliance posture. EU data handling and GDPR messaging make procurement easier for European teams.

For a list that is mostly clean and mostly made up of standard mailbox providers, Bouncer will get you a usable result. The trouble starts when your list contains the addresses that actually decide your bounce rate.

Where Bouncer stops: the “unknown” verdict

Most verification tools, Bouncer included, validate a mailbox by opening an SMTP conversation with the receiving server and asking, in effect, “does this inbox exist?” On a normal server you get a clear yes or no.

Catch-all domains (also called accept-all domains) break that model on purpose. A catch-all server is configured to accept mail for every address at the domain, whether the mailbox exists or not. So when Bouncer asks “does [email protected] exist?”, the server says yes. It would say yes to [email protected] too. The SMTP answer is meaningless, so Bouncer does the honest thing and returns “unknown” or “risky.”

That is technically correct behavior. The problem is what it leaves you holding. Catch-all configurations are common across B2B domains, Google Workspace tenants, and Microsoft 365 setups, which means a meaningful slice of your most valuable business contacts lands in that “unknown” pile. Bouncer then hands the decision back to you:

• Send to them anyway and risk hard bounces against addresses that do not exist, which damages your sender reputation.
• Suppress all of them and throw away real, reachable prospects who happen to sit behind a catch-all server.

Neither is a good outcome. You paid for verification and got back a shrug on the addresses that matter most. If you want a deeper walkthrough of why this happens, our guide on how to safely navigate risky or catch-all email addresses covers the mechanics in detail.

How Scrubby handles the same addresses

Scrubby was built specifically for the part of the list other tools give up on. Instead of stopping at the SMTP handshake, Scrubby uses a multi-step verification process that mimics real sending behavior to determine whether a catch-all mailbox is genuinely deliverable. The result is a real verdict (valid or invalid) on addresses that Bouncer would have returned as “unknown.”

In practice that changes the math on a list:

1. You recover real prospects. Addresses that would have been suppressed as “risky” get confirmed as valid, so you can actually email them.
2. You drop the dead ones with confidence. Catch-all addresses that are not deliverable get marked invalid before they ever hit your sequence, protecting your bounce rate.
3. Your “unknown” column shrinks dramatically. Decision-making stops being a coin flip.

A useful way to think about it: Bouncer is excellent at the deterministic layer of validation, while Scrubby is purpose-built for the probabilistic layer that begins where catch-all servers refuse to answer. The two are solving different parts of the same problem.

A practical workflow

You do not have to treat this as an either-or religious decision. Many teams run a hybrid model:

• Use a fast, cheap pass (Bouncer or any standard verifier) to clear out the obvious junk: bad syntax, dead domains, role accounts, and known spam traps.
• Route everything that comes back as “unknown,” “catch-all,” or “accept-all” through Scrubby to get a definitive verdict.

This keeps your per-check costs low on the easy 70 to 80 percent of a list while making sure the hard 20 to 30 percent, the part that quietly drives your bounce rate, gets resolved instead of guessed. If you are validating lists before cold outreach specifically, pairing clean data with a deliverability-first sending tool like Kali for calendar-based outreach is a natural next step once your list is verified.

When switching to Scrubby actually pays off

Be honest about your list before you switch anything. Scrubby is worth it when:

• A large share of your contacts are B2B addresses on Google Workspace or Microsoft 365, where catch-all setups are common.
• Your current tool returns a high percentage of “unknown” or “risky” results that you cannot act on.
• You run cold outreach or high-volume campaigns where every avoidable hard bounce chips away at domain reputation.
• You have already been suppressing catch-all addresses wholesale and suspect you are leaving real prospects on the table.

If your list is mostly consumer Gmail and Yahoo addresses with very few catch-all domains, you may not need the extra step, and Bouncer alone might be fine. The value of Scrubby scales with how many catch-all and accept-all addresses sit in your data.

The bottom line

Bouncer is a capable verifier for the deterministic checks, and it is reasonable to keep it in your stack. But “unknown” is not an answer you can build a campaign on, and catch-all addresses are too common in B2B to keep guessing about. Scrubby exists to turn that unknown column into clear valid and invalid verdicts, so you send to the people who are actually reachable and protect your sender reputation from the ones who are not.

If catch-all emails are the part of your list that keeps tripping up your verification tool, that is exactly the gap Scrubby was built to close.