How to spot fake “validation” services that only check syntax?

Some "validation" tools aren't really validating anything. They check whether an email address is formatted correctly (has an @ sign, a domain, the right structure) and call that valid. A syntax check takes milliseconds and requires no network connection. Real validation requires connecting to the receiving mail server. That takes longer, costs more to run, and is harder to build. So a number of cheap or free services skip it entirely.

Here's how to spot them:

• Results come back instantly at scale. If you upload 50,000 addresses and the results appear in seconds, the tool almost certainly didn't do server-level checks. SMTP verification takes time because it has to make real network connections.
• Almost everything comes back "valid." A syntax-only checker will return 95%+ valid on most real-world lists, because most addresses are formatted correctly. A real checker will typically flag 10-30% of lists as catch-all, risky, or invalid depending on list age and source.
• No "unknown" or "catch-all" category. Real validation tools surface catch-all addresses separately because they can't be confirmed either way. A tool that only returns valid/invalid is probably not doing the deeper checks.
• No disposable domain detection. Services like Mailinator, Guerrilla Mail, and hundreds of others provide throwaway addresses. A real validator flags these. A syntax-only tool treats them as valid.
• The price is suspiciously low. Running real SMTP verification at scale costs money. Very cheap services are often making that up somewhere, either by selling your data or by not doing the actual validation.

You can test a service easily: submit a list with a handful of known-invalid addresses (a domain you control with no MX records, or a mailbox you know doesn't exist). If they come back "valid," the service is only checking syntax.

If you're not sure which validation tool to trust, ask us and we'll give you a straight answer for your situation ;)