How to use the Email Validator
Choose a single address or a bulk list, then read the checks below the input. The results identify local-part, domain, quoting, character, and length errors. A valid syntax result does not show that a mailbox exists.
- Select Single Address and type a value in Email address, or select Bulk Addresses and paste entries into Bulk email addresses.
- For one address, enable Optional domain check (offline heuristic - not authoritative) or Optional DNS check (live MX/A lookup - not a deliverability guarantee) when needed.
- Read the result below the input. Bulk results show Address, Status, Duplicate, and Errors for each entry.
- In bulk mode, select Copy CSV or Download CSV after reviewing the rows.
How to validate an email address
The validator trims whitespace at the start and end before checking an address. It leaves the address text unchanged. A space inside the address is an error unless it is inside a properly quoted local-part.
Input: [email protected]
Output: Normalized address: [email protected]
Valid syntaxThe local-part can use dot-separated atoms or a quoted string. Checks cover allowed characters, leading or trailing dots, consecutive dots, quoted-string escaping, and the 64-character local-part limit.
Bulk email validator results and duplicates
Bulk email addresses accepts one entry per line or comma-separated entries. Empty entries are ignored. Each non-empty value gets a result row. Bulk validation does not run the optional domain or DNS checks.
[email protected]
bad [email protected]
[email protected]
Row 1: Valid
Row 2: Invalid, contains whitespace inside the address
Row 3: Valid, Duplicate of row 1Duplicate comparison lowercases the normalized value, so case differences do not create separate entries. Duplicates stay in the table and receive an earlier row number. CSV output includes Original, Normalized, Valid, Duplicate Of Row, and Errors.
- The domain is checked label by label for letters, digits, interior hyphens, dots, and label length. A regular domain must contain a dot. Bracketed address literals are checked for an IPv4 or IPv6-like shape, without deeper validation.
- The domain can be at most 255 characters, and the full address can be at most 254 characters.
- Empty input produces no result in either mode. A single-label domain, such as
user@localhost, receives a domain error.
Email domain checks and DNS lookup
The two optional checkboxes apply only to Single Address and start off. The domain check is an offline heuristic for a plausible letter-based final label. Its result is not authoritative.
The DNS check makes a live request to a public DNS-over-HTTPS resolver. It looks for MX records first, then an A record if no MX answer is found. The syntax checks run in the browser; enabling DNS sends the domain to the resolver. The lookup describes domain records, not a particular mailbox.
Where email validation comes up
Use Bulk email addresses when each pasted value needs its own status, duplicate flag, and error text. Review the table before selecting Copy CSV or Download CSV.
For one test, enter a value in Email address and inspect the Local-part, Domain, and error rows in the result.
Enable Optional DNS check (live MX/A lookup - not a deliverability guarantee) when a live domain lookup is needed. The result concerns the domain's records.
When another data validator fits better
Data Validation Tools is the parent category when the submitted value is not an email address. Use URL Validator, Parser & Checker when you need to inspect a URL's scheme, hostname, path, query parameters, or fragment. Use IBAN Validator for country prefix, expected length, BBAN structure, and the MOD-97 checksum. For country, number type, validity, or formatting results, choose Phone Number Validator & Formatter.
Frequently asked questions
How do I validate an email address?
Select Single Address, enter a value in Email address, and read the syntax result and error rows below it.
Can I validate a bulk email list?
Select Bulk Addresses and paste one address per line or separate addresses with commas in Bulk email addresses. Each non-empty entry receives its own result row.
Does valid email syntax mean the mailbox exists?
Valid syntax covers address structure only. The optional DNS check looks for domain MX records or an A-record fallback. It does not check a specific mailbox.
Does the email validator remove duplicate addresses?
Bulk duplicates remain in their original rows and are flagged with the earlier row number. Use Copy CSV or Download CSV to take the reviewed results elsewhere.