Bouncer: email verification software for marketing agencies
- Tested
- 957-address client list, 8 September 2026: results in 20 seconds; 874 deliverable, 54 risky, 20 undeliverable, 9 unknown and uncharged; 164 of 199 catch-all addresses resolved to deliverable. Classification accuracy and campaign bounce rates were not measured
- What it is
- Email verification and list hygiene: bulk cleaning, Email Verification API, Bouncer Shield for signup forms, AutoClean for CRM and ESP automation, Toxicity Check
- Designed for
- Pre-campaign cleaning, ESP and CRM migrations, reactivation, recurring hygiene across several clients
- Built for
- Agencies handling client data: EU processing, a published DPA, organisations with per-member permissions
- How it works
- Upload a CSV, connect a CRM or ESP, call the API, or check addresses at the signup form with Bouncer Shield. One credit per address
- Pricing
- $8 per 1,000 credits, falling to $2 at a million. Credits never expire; duplicates and unknown results are not charged
- Main consideration
- In the organisation we tested, credits were pooled and we found no per-member spending cap; Bouncer describes multiple organisations, teams and credit-access controls for separating clients
Who Bouncer fits
It fits marketing agencies whose sending risk sits on someone else's domain. A client hands over a database, the agency mails it, and any bounces land on the client's reputation rather than the agency's. Email verification for marketing agencies, and email verification for email marketing agencies in particular, is therefore a question of protecting sender reputation that belongs to the client.
That shape rewards graded output: a lifecycle team can hand a client a filtered segment with the trade-off worked out, rather than a cleaned file and a promise. The limit is scope: Bouncer verifies lists rather than building them.
| Stage | Bouncer feature | Agency use |
|---|---|---|
| Before a client campaign | Bulk verification, free list sampling | Client email list verification on a database the agency did not collect; segment by status and toxicity |
| During a migration | Bulk verification | Verify before importing into a new ESP or CRM, so the new platform starts clean |
| At the client's forms | Bouncer Shield or the Email Verification API | Stop typos and disposable addresses entering the client's database |
| Ongoing, per client | AutoClean | Automated email list cleaning on a connected CRM or ESP: new contacts checked hourly, existing ones re-verified on the configured schedule |
The stages and features are Bouncer's; the agency use column is ours.
What sets it apart, and what to weigh
The output is graded rather than binary, and catch-all addresses are resolved to a definite result where the infrastructure allows rather than swept into a risky bucket. The classification is deliberately cautious: Bouncer says it would rather return unknown than mark a possibly real address undeliverable, and does not charge for the unknowns that policy produces (Bouncer Guarantee). Against that, a cautious classifier leaves a small residue of unknowns for you to decide. They cost nothing, but nobody decides them for you.
Why list hygiene became a technical requirement
Two things changed at the mailbox providers, and both made email deliverability a technical condition rather than a marketing outcome. These are category facts about sending in general, not claims about Bouncer.
What is email verification for a marketing agency?
Email verification checks whether an address can receive mail without sending to it: valid syntax, a resolving domain, an MX record, a mailbox that accepts delivery. Email validation for agencies and email list cleaning for agencies are the same check applied to a client's file. For an agency the client's questions are commercial: which contacts can we mail safely, how many do we lose if we play it safe, and which are technically fine but risky?
A single yes or no cannot answer that. A status says whether an address is deliverable, undeliverable, risky or unknown. A reason code says why. A quality score grades confidence, and a toxicity score from 0 to 5, on a separate axis, flags spam traps, serial complainers and breached addresses: toxic email addresses that work and should still never be mailed. Email list hygiene is the recurring version of the same job, because contact data decays.
What should an agency do with each verification result?
Bouncer returns a status per address; separately, Bouncer Recommends turns status and toxicity into a configurable keep / suppress / quarantine label. The handling column below is common practice, not a rule.
| Status | What it means | Common handling |
|---|---|---|
| deliverable | The mailbox exists and accepts mail. It says nothing about consent or engagement | Keep, subject to the client's own consent and suppression rules |
| risky | Accept-all domain, full mailbox or disposable address: may bounce or may never be read | Follow the keep / suppress / quarantine label: by Bouncer's defaults, disposable and toxic addresses fall in suppress, accept-all and full mailbox in quarantine |
| undeliverable | The address or domain does not exist, or the server rejected it | Suppress from sends; keep the record if the client needs the history |
| unknown | The mail server did not answer in time. Not charged | Re-check later in bulk rather than delete |
Status definitions from Bouncer's integration guides and API documentation, read 11 September 2026. In Bouncer Recommends, keep covers safe addresses, suppress covers undeliverable, toxic and disposable, and quarantine covers everything between; the thresholds are configurable.
Tested by Cllimber
On 8 September 2026 we ran a 957-address client list through Bouncer on an account the company had credited with 25,000 credits. The file was consumer-heavy: 96.2% free-provider addresses across 62 domains, more than half Google-hosted. It is the same 957-address dataset used in Cllimber's ecommerce review of Bouncer, interpreted here for agency workflows. Each step was logged with start and end times and a screenshot.
Before spending anything, the upload screen ran a free pre-check: 957 addresses, one invalid format, no duplicates, 62 domains, 306 estimated toxic addresses and a 4.3% bounce estimate. Bouncer's free list sampling page does the same on a random sample with no login, enough to tell whether a full clean is needed before quoting for one.
| What came back | Result |
|---|---|
| Upload to results, 957 addresses | 20 seconds, stopwatch |
| deliverable | 874 (91.3%) |
| risky | 54 (5.6%) |
| undeliverable | 20 (2.09%) |
| unknown | 9 (0.94%) |
| Coverage | 948 of 957 = 99.06% |
| Credits charged | 948 of 957, nine refunded |
Cllimber hands-on test, 8 September 2026. Bouncer publishes 98% coverage with approximately 2% or fewer unknown; this run came in ahead of that. Accuracy was not measured: no seeded control addresses, no send afterwards.
Each result row carried the status, a reason code, a quality score, a toxicity score and flags for disposable email detection, role-based, free-provider, full-mailbox and catch-all addresses, and every column came through in the export. The run covered bulk email verification, pre-check, results, organisations and filtered export. Nothing failed. AutoClean, the API and Bouncer Shield were not tested and are described below from Bouncer's own pages.
Catch-all email verification, and what a result on one looks like
A catch-all domain accepts mail for any address, so a mailbox check alone cannot tell whether a given mailbox exists. Our list was 20.8% catch-all, 199 of 957 addresses on accept-all domains, and of those 164 were classified deliverable; 31 were risky, two undeliverable and two unknown. We did not verify those classifications by sending, so this is a count of what Bouncer returned, not a measure of its accuracy. Bouncer credits deeper verification of Google-hosted and Microsoft-hosted catch-alls, addresses behind anti-spam infrastructure and niche providers.
Verifying multiple client lists and team access
A member can be invited into an organisation with permission tags covering verification and API access, and gets their own login. Each upload is its own job with its own results and export, so several client lists sit side by side without mixing. In the organisation we tested, credits sat in one pool and the invite controlled which features a member could use; we found no per-member spending cap. Bouncer describes multiple organisations and teams per account, with credit access and usage controlled at organisation level, which is the route it offers for keeping clients apart. We tested one organisation, not several.
What can an agency report to a client after verification?
Everything below comes from our 8 September run and is the kind of summary an agency can hand a client the same day. The bounce figures are Bouncer's estimates before any send; campaign results were not measured.
| Line in the client report | From our run |
|---|---|
| Addresses checked | 957, in 20 seconds |
| Status breakdown | 874 deliverable (91.3%), 54 risky (5.6%), 20 undeliverable (2.09%), 9 unknown (0.94%) |
| Unknown results | 9, not charged, to be re-checked later |
| Credits charged | 948 of 957 |
| Selected export size | 915 at the Maximum audience preset; 601 at Maximum safety; presets editable |
| Bouncer's estimated bounce rate | 4% on the full list; 1.6% at 915; 0.6% at 601 (estimates, not measured campaign results) |
Cllimber hands-on test, 8 September 2026. Every line is exportable from Bouncer's results and export screens; the export builder shows the estimate for whichever rule set the agency selects.
Bouncer by the numbers
| Figure | What Bouncer publishes |
|---|---|
| Accuracy | Above 99% overall; 100% on undeliverable specifically, a separate claim covering only the addresses it rules out |
| Coverage | 98%, with approximately 2% or fewer unknown |
| The guarantee | A credit or refund where an address returned deliverable bounces within 72 hours for a qualifying reason |
| Speed | Up to 200,000 addresses per hour per customer |
| Reviews | 4.8 from 337 reviews on G2; 4.9 from 318 on Capterra (both read 11 September 2026) |
| Company | Founded 2017, Wrocław, Poland, EU infrastructure; organisations and teams with per-organisation credit control; human support at every account size; zero-downtime policy, status.usebouncer.com |
Email verification for Klaviyo agencies and HubSpot teams
Bouncer connects to the platforms agencies run client programmes on. On 11 September 2026 its integrations page listed 25 connectors, including HubSpot, Klaviyo, Mailchimp, Brevo, MailerLite, GetResponse, Pipedrive, and the automation platforms Make, Integrately, Pabbly and OttoKit. On Klaviyo, a list is imported, verified and exported back, either by removing chosen statuses or by writing a bouncer_recommends property (keep, suppress or quarantine) onto each profile so a flow can branch on it. Anything without a connector reaches Bouncer through the Email Verification API.
Can Bouncer automatically clean a client's Klaviyo or HubSpot list?
Yes, through AutoClean, which is automated email list cleaning on a connected platform, left running. What follows is from Bouncer's AutoClean page, read 11 September 2026; we did not run it.
Initial verification. When AutoClean is switched on for a list, whole-list verification on setup is a configurable option.
Hourly checks of new contacts. AutoClean checks new contacts hourly.
Scheduled re-verification. Existing contacts are re-verified on the configured schedule, set in days per list.
Configurable actions. Each run applies the keep / suppress / quarantine rules and writes the result back, so the client's platform can act on it. Jobs show creation date, last run and next run, and can be paused, edited or removed.
AutoClean is listed for HubSpot, User.com, Klaviyo, Brevo, Mailchimp and Inboxroad. For an agency running hygiene across several client platforms, new contacts are checked hourly and existing contacts are re-verified on the configured schedule, rather than verification being a monthly manual job.
Reactivating an old client database
A practical sequence when a client asks whether a dormant list can be mailed again: verify the whole file; review the risky and unknown results rather than deleting them; build segments from the statuses or the keep / suppress / quarantine labels; and keep the client's existing consent and suppression lists in force as well, since a deliverable address is not a consenting one. What the standard advice never says is how much of the list you give up at each level of caution. Bouncer's export builder answers it: six preset filter positions, each with a live bounce estimate across the whole list (an estimate, not a measured rate).
| Filter position | Addresses kept | Bounce estimate |
|---|---|---|
| All results | 957 | 4% |
| Maximum audience | 915 | 1.6% |
| Position 3 | 910 | 1.3% |
| Position 4 | 864 | 1.1% |
| Position 5 | 605 | 0.6% |
| Maximum safety | 601 | 0.6% |
Cllimber hands-on test, 8 September 2026. The pre-check showed 4.3% before verification and the export builder 4% after; both recorded as read. Presets are editable and custom rule sets can be saved.
Giving up 42 addresses takes the estimate from 4% to 1.6%, while moving from position 4 to 5 costs 259 addresses for half a percentage point. The same table sizes an ESP or CRM migration before the first send, which is one way of reducing email bounce rates on the new platform from day one. Toxicity runs on a separate axis: 273 addresses classed deliverable are still excluded at the strictest setting on toxicity grounds, and every address scoring 4 or 5 came back risky rather than undeliverable. That is where the suppress label does its work: by Bouncer's defaults, toxic addresses are suppressed from sends while the record is kept.
Bouncer's own case study is YOCTO, a lifecycle agency reactivating legacy databases for US DTC brands: 90,960 dormant customers re-engaged at a reported $4.56 each, with legacy lists segmented rather than mailed in full. Those are Bouncer's figures, not verified by us.
"For high-scale reactivation cases like ours, Bouncer is a complete no-brainer."
How it differs from the other kinds of tool
The distinction that matters for an agency is where the list comes from. Hygiene features inside a client's ESP or CRM act on what is already in that platform; a standalone platform treats any list from any source the same way, including a CSV handed over before onboarding, and returns enough detail to advise on it. The cost is another vendor, contract and DPA in the chain. Standalone tools also differ on whether credits expire, whether unknowns are charged and where data is processed. Bouncer's answers are never, no, Frankfurt.
Getting started
A free account at app.usebouncer.com/signup includes 100 credits with no card, enough to sample a client list and read every output column. Lists go in by CSV, paste, integration or API; paid credits start at a 1,000-credit minimum; Bouncer Shield, for a client's signup forms, is a separate monthly subscription priced on monthly check volume.
What it costs per thousand, and whether credits expire
Third-party sites publish inconsistent figures for Bouncer's pricing; Bouncer's own brief to us says the same and asks that pricing be taken from its pricing page. The ladder from Bouncer's pricing page, read 9 September 2026:
| Credits | Price | Per 1,000 |
|---|---|---|
| 1,000 | $8 | $8.00 |
| 10,000 | $60 | $6.00 |
| 50,000 | $250 | $5.00 |
| 100,000 | $400 | $4.00 |
| 250,000 | $750 | $3.00 |
| 1,000,000 | $2,000 | $2.00 |
Matching the in-product purchase screen the same day. One credit verifies one address; the API uses the same credits. Check the pricing page for current figures.
Two terms matter more than the headline rate. Pay-as-you-go credits do not expire, which is not a given in this category: some tools void unused credits after a fixed window. And unknown results are not charged, which we watched rather than read: the counter read 25,100 before the run, 24,143 with all 957 credits held up front, and 24,152 on completion. Nine came back, matching the nine unknowns. Duplicates within a list are not charged either.
GDPR-compliant email verification: EU hosting, and who the processor is
The client owns the list and decides why it is processed: the controller. The agency acts on those instructions: the processor. The vendor sits beneath the agency as a sub-processor, and each link needs a Data Processing Agreement.
Bouncer's DPA states where processing happens: on AWS in the Frankfurt region, with no transfer outside the EU. Only the email address is required; data is stored up to 60 days, then anonymised and deleted, or deleted on demand through an API function; breaches are notified within 72 hours; a data protection officer is named; the agreement is governed by Polish law. Bouncer's GDPR page adds that addresses are hashed except at the layer results are retrieved from. EU-hosted email verification with a published DPA is what an agency needs to put in its own DPA with the client.
Is Bouncer suitable for marketing agencies?
The clearest fit is an agency that receives client databases it did not collect and has to mail them safely: lifecycle and retention agencies reactivating old files, CRM and automation agencies migrating clients between platforms, and Klaviyo or HubSpot agencies that want hygiene running on each client's account without a monthly manual job. Each maps to a stage in the workflow table above. Client separation runs through Bouncer's organisations and teams, with credit access controlled per organisation; within the single organisation we tested, credits were pooled and no per-member cap was found. An agency that only ever mails its own list will use a fraction of this.
What Bouncer is not designed as
- A contact database. It verifies lists you hold; it does not build or source them
- A deliverability guarantee. Authentication, sender reputation, content and engagement all still matter, and a valid address is not necessarily an engaged or consenting one
- A client billing system. Organisations and credit-access controls separate clients; invoicing them for verification is the agency's job
Considerations before adopting
- Automation depth depends on the client's stack. AutoClean covers HubSpot, User.com, Klaviyo, Brevo, Mailchimp and Inboxroad; other platforms mean the API or an automation platform
- Volume pricing rewards consolidation. Buying per client at 1,000 credits a time costs four times the million-credit rate
- Real-time checks leave a few more unknowns than bulk checks. A check at a client's form has to answer in seconds, so when a mail server is slow Bouncer returns unknown rather than keep the visitor waiting; a bulk check can wait and resolve it. Bouncer puts the difference at about 5%. Unknowns cost nothing, so run a form's unknowns through a bulk verification from time to time
Email verification for marketing agencies, answered.
Does Bouncer verify catch-all emails?
On our test list it returned a classification for most. Of 957 addresses, 199 sat on catch-all domains; 164 were classified deliverable, 31 risky, two undeliverable, two unknown (8 September 2026). We did not test those classifications by sending.
Should an agency verify a list before every campaign?
There is no universal interval; the triggers are. A list the agency has not mailed before is verified before the first send. A list being moved to a new ESP or CRM is verified before import. A dormant list is verified before reactivation. A list that grows every day is re-verified on the configured schedule, which AutoClean sets in days, with new contacts checked hourly. Between those, Bouncer's free sampling page shows whether a full clean is needed at all.
Does Bouncer charge for unknown results, and do credits expire?
No to both. On our run nine credits were refunded on completion, matching the nine unknowns; duplicates within a list are not charged either. Pay-as-you-go credits do not expire.
Is Bouncer GDPR compliant, and where does it process data?
Bouncer publishes a DPA specifying AWS in the Frankfurt region with no transfer outside the EU; data is deleted after 60 days or on demand, and breaches are notified within 72 hours. The client is controller, the agency processor and Bouncer sub-processor, so each link needs a DPA.
Can email verification be automated for Klaviyo or HubSpot?
Yes, through AutoClean, which can verify a connected list on setup, checks new contacts hourly, re-verifies existing ones on the configured schedule, and applies keep, suppress or quarantine rules. It is listed for HubSpot, User.com, Klaviyo, Brevo, Mailchimp and Inboxroad.
How can an agency protect a client's sender reputation before a campaign?
Remove the bounces before they happen. On our 957-address client list, 20 addresses were undeliverable and 54 risky before any send, and the export builder showed the trade-off at each level of caution: 957 at a 4% bounce estimate, 915 at 1.6%, 601 at 0.6%. Verification is one component; authentication, content and engagement still matter.
Can marketing agencies resell Bouncer, or build verification into their own service?
Three routes: price verification into a hygiene or deliverability retainer; refer or resell through Bouncer's Agency Partner Program; or automate it into a client's CRM through AutoClean and sell a standing process.
What should a marketing agency check before choosing an email verification tool?
Six things. Whether unknown results are charged. Whether credits expire. What happens to catch-alls, where you want a count of definite results rather than a policy. Where data is processed and whether a DPA is published. How deep the automation goes. And whether the output includes reason codes, scores and risk flags, because a status alone forces binary decisions.
Sources: Cllimber hands-on test, 957-address list, 8 September 2026, on an account credited by Bouncer, logged with times and screenshots. Bouncer's figures are from its own pages and documentation, read 9 to 11 September 2026: the Bouncer Guarantee, pricing, integrations, AutoClean, Bouncer Shield, GDPR and DPA pages at usebouncer.com, the YOCTO case study, the Agency Partner Program page, and the real-time verification reference at docs.usebouncer.com; pricing cross-checked against the in-product purchase screen. Review counts from G2 and Capterra, read 11 September 2026. Google and Microsoft requirements linked above.
Bouncer
Product pages, pricing, documentation and the DPA referenced in this article are published at usebouncer.com. Signup includes 100 free credits with no card required.