We're using a proprietary multi-layered algorithm that combines a series of criteria, checks, and heuristics to assess each email address.

It includes:

Format and domain-level validations SMTP-level interaction with fallback logic Detection of disposable domains, catch-all behavior, and risky patterns A scoring model that returns both a risk label (valid, risky, invalid) and a confidence score (0.0 to 1.0) And much more — especially for nuanced edge cases and deliverability signals

Unlike many validators that return a binary result, MailShrimp gives you both a label and a score, so you can decide what’s safe to keep based on your own thresholds.

We're also focused on speed and usability. Our logic is designed to handle edge cases often missed by more generic tools.

Still early stage — feedback is very welcome!