Invalid 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: 79.9% are mail-enabled, but only 22.6% 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.