Why Results Can Differ Between Tools
Why email verification results can differ between tools and why differences are expected, not errors.
It is normal for email verification results to differ between tools.
Email verification is not an exact science.
Email Servers Do Not Behave Consistently
Email verification relies on how recipient servers respond.
Those responses can change based on:
Two tools can test the same email and receive different responses.
Catch-All Domains Are the Biggest Variable
Many business domains are configured as catch-all.
This means:
The server accepts all emails
Valid and invalid addresses appear identical
Basic SMTP checks cannot distinguish them
Some tools label all catch-alls as risky.
CSVgo runs additional validation steps to reduce uncertainty, but some variability will always remain.
Security Gateways Affect Results
Modern email systems use:
Secure Email Gateways (SEGs)
Conditional Non-Delivery Reports
These systems may:
Accept emails but drop them later
Reject verification probes but accept real sends
Hide mailbox existence by design
Different tools interpret these signals differently.
Not all tools perform the same checks.
Differences may include:
Number of verification signals used
How aggressively retries are handled
How greylisting is interpreted
How false positives are filtered
CSVgo combines multiple signals instead of relying on a single test.
Real-World Sending Is the Final Test
Verification predicts deliverability.
It does not guarantee it.
Actual results depend on:
Your sending infrastructure
Domain age and reputation
Sending volume and pacing
This is why testing is always recommended.
Why CSVgo May Show More Deliverable Emails
CSVgo often returns:
Higher deliverable counts
Fewer emails stuck in “risky”
This happens because:
Catch-alls are validated instead of discarded
ESP behavior is considered
Multiple verification signals are combined
More data does not mean more risk when used correctly.
How to Interpret Differences Safely
Best practice:
Start with conservative exports
Test in controlled batches
Observe bounce and reply rates
Adjust ESP segmentation over time
CSVgo gives you options so you can choose your risk level.
Differences between tools are expected.
What matters is:
Control over what you send
CSVgo is built to give you better inputs and let you decide how to act on them.
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