Head-to-head against published features, last reviewed 29 June 2026.
Validation tools answer one question: does the mailbox exist? That is
the SMTP acceptance check, and we do it too. The gap is everything
that happens after the 250 OK.
We cross-check every address against engagement decay
signals, sender reputation history,
domain infrastructure quality (MX records, hosting
patterns, WHOIS age), and a decade of receiver-side behavior we have
watched and codified.
A valid address can still be a chronic complainer, sitting on a domain
whose MX rotated last week, or already so saturated with other senders
that your next send will land in spam. Those are the rows that torch
your sender reputation, and the rows your current validator marked safe.