Bulk email verification checks a file of email addresses before a campaign or import. It removes malformed and clearly invalid addresses, identifies risky cases, and keeps unknown results separate. It does not create permission to contact people and should not be used to make purchased or scraped lists acceptable.
Mailthentic accepts CSV and XLSX files through the active bulk workflow. Job size is limited by account tier, credit balance, and runtime settings. There is no published MB limit.
From source file to export
- Define the audience. Start with addresses collected for a legitimate purpose. Apply opt-outs and suppression lists first.
- Prepare one clear email column. Keep a contact ID beside it when results must return to a CRM.
- Upload CSV or XLSX. Mailthentic detects a likely email column, normalizes addresses, and processes each unique address once.
- Wait for the job. It can be queued, running, analyzing, done, or failed. A failed job does not mean every address is invalid.
- Review the four buckets. Valid, risky, invalid, and unknown require different actions.
- Export CSV or XLSX. Keep the full audit output as well as any filtered send list.
CSV preparation example
contact_id,email,source,consent_status
crm_1842,alex@example.com,webinar,confirmed
crm_1843,sales@example.org,customer_request,confirmed
crm_1844,alex@example.com,webinar,confirmed
The repeated address is processed once while both CRM records stay in the source data. Do not put several addresses in one cell. Keep the header row and save a UTF-8 CSV when possible.
Read the output
| Bucket or signal | Meaning | Typical action |
|---|---|---|
| Valid | The detailed status can be confirmed or deliverable but unconfirmed. | Inspect the stored status before treating every row alike. |
| Invalid | Syntax, disposable domain, domain, MX, or a clear recipient response failed. | Suppress or correct the source record. |
| Risky | The result can include catch-all or missing authentication signals. | Segment and apply a documented risk policy. |
| Unknown | No reliable decision was available, often because of a temporary condition. | Retry later or exclude from a time-sensitive send. |
| Role-based | The local part represents a function such as sales or support. | Keep it only when a shared inbox is the intended audience. |
| Catch-all | The domain accepts a random control recipient. | Use acquisition and engagement evidence. |
A confidence score summarizes signals. It is not a guarantee of delivery. A mailbox can become full, be disabled after checking, or filter a future message.
What supports the verdict
The workflow can evaluate syntax, domain and MX resolution, disposable-domain data, role local parts, SMTP responses, catch-all controls, known bounce signals, and available SPF, DKIM, and DMARC information. An MX record shows a route, not mailbox existence. The domain health checker audits a domain rather than cleaning a list.
Read the role-based address guide and catch-all guide before automating suppression.
Bulk upload or API?
| Situation | Fit | Reason |
|---|---|---|
| CRM export before a campaign | Bulk | The file exists and needs reviewable output. |
| Signup form | API | The decision belongs in the application workflow. |
| Old database plus new capture | Hybrid | Clean once, then verify at entry. |
| One record investigation | Single checker | A file or integration adds no value. |
Use the API versus bulk guide for the full decision, or go to the API page for actual endpoints.
Before sending
- Apply opt-outs, complaints, and prior hard bounces.
- Quarantine unknown results instead of forcing a verdict.
- Keep the verification date because addresses change.
- Do not treat cleaning as a substitute for consent or sender authentication.
Upload a permission-based list
Open the Bulk Email Verifier. For one address, use the free email checker.
Ready to verify your email list?
Start free with 50 verification credits. No credit card required.