TL;DR
- Compare cost per usable result, not list price: include unknowns, duplicates, expiry and subscriptions.
- Check the terms that cost money later: credit expiry, unknown-result charging and minimum purchases.
- Test on your own list. Published accuracy figures aren't comparable.
- Make sure it fits how you work: bulk upload, API, real-time form check or all three.
Ten questions to ask
- What does it cost per 1,000 at my volume? See cost per 1,000.
- Do credits expire? If so, when, and does a subscription change it?
- Are unknown results charged or refunded?
- Are duplicates charged?
- How does it treat catch-all domains? Flagged risky, or marked deliverable?
- Is there an API, and what are its limits? See APIs compared.
- How fast is bulk verification? Vendor speed claims vary; ask for your size.
- What are its security and data-handling terms? How long are uploaded lists kept?
- Is there a free test large enough to be meaningful?
- What does support look like? Chat, email, response times?
Red flags
- No public prices and a mandatory demo, when you only want to buy credits.
- Accuracy claims with no definition (is unknown a miss? is catch-all deliverable?).
- Credits that expire quickly with no refund route.
- Charging for unknowns, which means paying for answers the tool couldn't give.
- Lock-in through bundles you won't use.
A simple scorecard
| Criterion | Weight | How to score |
|---|---|---|
| Cost per usable result | High | Price / deliverable results from your sample |
| Terms (expiry, unknowns, duplicates) | High | Read them, then ask support |
| Result quality | High | Blind test on 500 addresses |
| Fit (API, bulk, widget) | Medium | Does it cover your workflow? |
| Security and compliance | Medium | Stated certifications, retention policy |
| Support | Low-medium | Test it with one question |
Run the test described in how to test an email verifier on two or three finalists.
If you do cold email
Prioritise catch-all handling, credits that don't expire (campaign volume is lumpy) and the ability to re-verify before follow-ups. See best verifier for cold email.
FAQ
What should I look for in an email verifier?
Cost per usable result, credit expiry and unknown handling, catch-all treatment, an API that fits your stack, and results from a blind test on your own list.
How do I compare email verification vendors?
Use the same 500-address sample on each, tabulate the result categories, and compare cost per deliverable address.
Do I need a verifier with an API?
If you verify at signup or inside your tools, yes. For occasional list cleaning, bulk upload is enough.
Related
- Best email verification services
- Pricing models explained
- All comparisons
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