Email Validator: Check Address Syntax
Use the Email Validator to check supplied addresses one at a time or as a list. It checks local-part, domain, quoting, invalid characters, and length, then reports errors without removing entries. A valid syntax result does not confirm that a mailbox exists or can receive mail.
What the Validator Checks
Surrounding whitespace is trimmed before an address is checked. Whitespace inside an address is reported unless it is properly inside a quoted local-part.
- The local-part supports dot-atom or quoted-string structure. The tool checks allowed characters, dot placement, quoting, and the 64-character local-part limit.
- The domain is checked label by label for allowed characters, dots, hyphens, label length, overall length, and normal-domain dot placement. Bracketed address literals such as
[192.168.1.1]are recognized structurally but not deeply validated. - The full address is checked against the 254-character limit. The domain limit is 255 characters.
Single Address and Bulk Addresses
The visible modes handle different workflows:
- Single Address shows a status and field breakdown for one value. Empty input shows Enter an email address above.
- Bulk Addresses accepts non-empty entries separated by new lines or commas. Results show Address, Status, Duplicate, and Errors. Empty input produces no result rows.
Bulk validation does not run the optional domain or DNS checks.
Optional Domain and DNS Checks
Both checkboxes are off by default and apply to Single Address only.
- Optional domain check is an offline heuristic that checks whether the final domain label resembles a plausible TLD. It is not authoritative.
- Optional DNS check makes a live request to a public DNS-over-HTTPS resolver. It checks MX records first and falls back to an A record when no MX answer is found. Network or resolver problems are reported as lookup failures.
Neither check confirms that a specific mailbox exists or is deliverable.
How to Validate an Address or List
- For one address, select Single Address, enter it in Email address, and the result updates automatically. Enable the optional checks first if needed.
- For a list, select Bulk Addresses and paste entries into Bulk email addresses, one per line or separated by commas.
- Paste the list into Bulk Addresses; results update automatically.
- Review the status, duplicate flags, and errors. In bulk mode, select Copy CSV or Download CSV after results appear.
Duplicates and CSV Results
Bulk duplicates stay in their original row positions. Comparison uses the normalized value case-insensitively, and a repeated value is marked Duplicate of row N. No rows are removed.
CSV output contains Original, Normalized, Valid, Duplicate Of Row, and Errors columns. Bulk entries are trimmed during parsing, so surrounding pasted whitespace is not preserved in the Original field. Download CSV uses the filename email-validation-results.csv.
Limitations and Data Handling
This tool checks syntax only. It does not confirm mailbox existence, activity, SMTP acceptance, or deliverability, and it does not remove invalid or duplicate addresses. Processing is local in the browser by default. Enabling the DNS check sends a live request to a public resolver; its result concerns domain records, not a specific mailbox.
Frequently Asked Questions (FAQs)
Does a "Valid syntax" result mean the mailbox actually exists?
No. The result covers address structure only. The optional DNS check looks for MX records or falls back to an A record; it does not confirm a specific mailbox.
How is this different from Clean Email List and Extract Emails?
Clean Email List removes or changes list entries. Extract Emails searches text for addresses. This validator checks addresses you supply and reports errors without removing them.
Does this tool remove invalid or duplicate addresses for me?
No. Invalid and duplicate addresses remain in the results. Duplicates are flagged rather than removed.
What do the optional domain and DNS checks do?
The domain check is an offline heuristic. The DNS check is a live lookup for MX records, with an A-record fallback. Both are off by default, apply only to Single Address, and do not confirm mailbox deliverability.