Syntax & MX validation
Catch malformed addresses and dead domains first.
What it does
Why it matters
Syntax and MX checks are the first line of defense — they catch obvious invalids and domains that can't receive mail at all, before any deeper (and slower) verification runs.
Syntax and MX checks are the cheap, fast first pass that removes the obviously broken before any deeper verification runs. They catch malformed addresses and domains that can't receive mail at all.
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Frequently asked
What does an MX check tell you?
Whether the domain has mail servers configured — if it doesn't, every address there will hard-bounce, so it's dropped early.
Isn't valid syntax enough?
No — a well-formed address can still be undeliverable; syntax is just the first filter before domain and mailbox checks.
Does it catch typos?
Obvious malformations, yes; provider typos like gmial.com are handled by the did-you-mean correction.
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