Use an email verification API when addresses enter one at a time and the product needs an immediate decision. Use bulk verification when you already have a file or database segment. Use both when you need to repair existing data and stop new errors at the source.
Decision table
| Requirement | API | Bulk |
|---|---|---|
| Signup or checkout | Strong fit | Poor fit |
| CRM export | Requires orchestration | Strong fit |
| Immediate feedback | Yes, with asynchronous handling | No |
| Spreadsheet context | You build the join | Reviewable CSV or XLSX export |
| Retry control | Your integration polls and retries | Managed by the job workflow |
| Engineering effort | Higher | Lower |
Real-time can still be asynchronous
Mailthentic's single endpoint creates a job and returns HTTP 202 with status and results URLs. A form should show a pending state, poll within a timeout, and decide what to do if the result stays unknown. Do not hold a checkout open indefinitely while a remote server defers.
A practical pattern rejects clear syntax and disposable failures, accepts confirmed results, and uses email confirmation for ambiguous providers.
Bulk is an operations workflow
A CRM import or old subscriber table already exists as a batch. Uploading CSV or XLSX lets an operator review counts, reasons, and result groups. Read the bulk guide for preparation and interpretation.
Realistic scenarios
SaaS signup
Run local syntax validation, create an API job, and poll briefly. Ask for confirmation when ownership matters.
CRM import
Export with a stable contact ID, use the bulk verifier, and join results back without reactivating opt-outs.
Database hygiene
Process controlled batches. Separate unknowns for retry and log each suppression rule.
Hybrid
Clean the old database once. Then place the API at capture boundaries.
Cost, latency, and retries
Both paths consume credits under current account rules. The operational cost differs. API work needs polling, timeouts, idempotency, and monitoring. Bulk needs a file handoff and a process for acting on output.
Retry HTTP 429 and transient 5xx responses with exponential backoff and jitter. Correct authentication, scope, payment, or format errors before retrying. Schedule unknown results later instead of issuing rapid duplicate probes.
Choose the smallest system
- Bulk for occasional campaign preparation.
- API for a product boundary.
- Hybrid for legacy data plus ongoing capture.
- The single checker for investigation.
Choose your workflow
Open the bulk verifier or read the API integration page.
Ready to verify your email list?
Start free with 50 verification credits. No credit card required.