MailTester NinjaInvalid email addresses waste money and wreck your sender reputation. Here is how to check an email address properly, in two layers, with free tools and no fluff.
Before a mailbox can exist, its domain has to be set up to receive mail (an MX record) and, ideally, authenticated (SPF and DMARC). Check any domain right here:
Context from our live scan of 50,000 domains: 80.4% are mail-enabled, but only 22.9% enforce DMARC with p=reject, so a domain "having email" says little about whether it is well configured.
A domain can accept mail while a specific address does not exist. Confirming the actual mailbox needs real-time verification: open an SMTP conversation up to the recipient step, read the answer, stop, without sending anything. That is exactly what MailTester Ninja does, and it stores nothing.
Yes. This page has a free domain checker (MX, SPF, DMARC). To verify whether a specific mailbox actually exists, MailTester Ninja offers free checks on its home page.
A checker inspects a domain’s configuration (does it accept mail, is it authenticated). A verifier goes further and confirms a specific mailbox is real and deliverable by talking to the mail server, without sending anything.
Yes. Real-time verification opens an SMTP conversation up to the recipient step and reads the server’s answer, then stops. No message is ever delivered, and MailTester Ninja stores nothing.
A catch-all domain accepts mail for every address, so no tool can be certain a specific mailbox exists there. Honest tools label these "catch-all / uncertain" rather than pretending they are valid.
Free tools: Deliverability Analyzer · SPF/DMARC Generator · Email Infrastructure Index.