MailTester Ninja

MailTester Ninja helps companies keep their contact data clean, so that campaigns, sales sequences and transactional messages reach real people.

The approach is direct: rather than consulting a stored list of known addresses, the service contacts the mail server responsible for each address at the moment of the request. It validates the syntax, looks up the domain and its MX records, and runs a brief SMTP dialogue that ends before any content is transmitted. The outcome is sorted into three groups, deliverable (ok), undeliverable (ko) and uncertain (mb), with a reason attached, for example Rejected, Catch-All, Disposable or No MX. Uncertain cases are never rounded up to deliverable. Organisations that run their lists through it report bounce rates below 1%.

Teams can work in the browser, uploading a file or pasting addresses and downloading the outcome, or through a REST API designed for automation: a single GET call per address, JSON responses, an OpenAPI 3.1 contract, official client libraries for Python and JavaScript, and integration guides for workflow tools such as Zapier, Make and n8n. The same account also gives access to an email finder that proposes a likely business address for a named contact at a given company.

Privacy is built in: the addresses submitted are processed for the check and not retained afterwards, in line with GDPR.

Commercially, the product follows a subscription model instead of prepaid credits. A free tier lets teams evaluate it. The weekly Starter plan ($6.99) and the monthly Pro plan ($23.99) each cover 100,000 checks daily, Ultimate ($39.99 monthly) doubles that to 200,000, and the daily limit can be raised further.

MailTester Ninja is developed and run by Unlimited & Limited in London, United Kingdom, and has been in operation since 2018.