Email Validator
Checks the syntax of an address in your browser, and on request whether its domain is disposable and can receive mail.
How Email Validation Works
What is Email Validation?
Three different questions get called validation. Whether the address is written correctly, whether the domain can receive mail at all, and whether that particular mailbox exists.
The first two are answered here. The third cannot be answered honestly without sending mail: a server that replies to a probe is telling you about its configuration, not about the mailbox, and many accept everything on purpose.
How to Use
- Type the address. The syntax is checked as you type, in your browser, and the character that is wrong is marked.
- Check the domain is a separate button because it sends the domain, and only the domain, to this site's server. The part before the @ never leaves the browser.
- Turn on Mail security records to add SPF, DMARC, MTA-STS, TLS-RPT, BIMI and DANE. That is six more DNS queries, so it is off by default.
- A list checks the syntax of many addresses at once and marks repeats. It makes no network requests at all.
What Gets Checked
| Grammar | RFC 5322, including quoted local parts and address literals in brackets |
| Lengths | RFC 5321: 64 characters before the @, 255 after it, 254 in total |
| Labels | No leading or trailing hyphen, at most 63 characters, no all numeric top level domain |
| Disposable | Against a list of about 8,000 throwaway domains, kept in a database and refreshed from its source |
| Delivery | MX records, and the address record that RFC 5321 allows when there is no MX |
Important Notes
- Valid syntax says nothing about whether anyone reads mail there. The two answers are separate on this page for that reason.
- The syntax check follows the grammar and stops there. Whether a one letter top level domain exists is not something the grammar decides, and the domain check answers it properly.
- A disposable domain is not a broken one. Plenty of people use one deliberately, and the list is maintained by hand, so it is neither complete nor beyond dispute.
- A role address such as
info@orsupport@is perfectly valid. It is worth knowing because it usually reaches a team rather than a person.
Privacy & Security: the syntax check runs entirely in your browser. Only the domain check contacts a server, and it sends the domain alone, never the part before the @ and never the whole address.
The address
The domain
This is the only part that leaves your browser, and it sends the domain by itself. It looks the domain up in a list of throwaway providers and asks DNS whether it can receive mail.