Email list syntax cleaner and deduplicator
Remove duplicate entries, whitespace and obviously malformed addresses.
Your inputs
Your results
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How it works
Trim entries, remove optional display names, lowercase domains, and remove repeated addresses while keeping an audit of the decisions. The conservative default treats Ada@example.com and ada@example.com as separate addresses. Choose case-insensitive comparison only when appropriate for your list. Download the clean text list for review or the CSV audit to investigate skipped entries.
Read the source reference ↗A few things to know
Supports common ASCII dot-atom addresses with dotted domains. This is a conservative subset of email syntax, not full RFC validation: quoted local parts, comments, Unicode addresses, domain literals and single-label domains are flagged for manual review. Newlines always separate entries. This does not parse a multi-column contact CSV, verify consent, detect typos in provider names, or determine whether an address receives mail. Gmail dots and plus aliases are never combined. A kept entry may still bounce, and an unsupported entry may be legitimate. List membership and unsubscribe state are outside this tool.
When to use this tool
An email list cleaner can remove repeated entries and obvious syntax problems before an import. This tool trims entries, extracts supported display-name formats, lowercases domains and produces an audit of every decision. Its conservative default preserves local-part case. A retained address has passed the supported syntax checks only: the cleaner does not contact a mailbox, determine consent or promise that the address will receive mail.
- Clean a one-column address list before reviewing a newsletter import.
- Remove repeated contacts while retaining a downloadable decision audit.
- Separate malformed or unsupported entries for manual investigation.
How to use email list syntax cleaner and deduplicator
Paste the address entries
Separate addresses with newlines or commas. Supported display names can use Name <address>, including quoted names containing commas. Paste address entries rather than a multi-column contact CSV.
Choose duplicate comparison
Preserve local-part case unless you know whole-address case-insensitive comparison suits your system. Domains are always compared without case. The first matching address keeps its original local-part spelling.
Review the audit before importing
Inspect kept entries, duplicates and syntax or unsupported cases. Download the clean text list and audit CSV. Resolve legitimate unsupported formats manually, and preserve your own consent and unsubscribe controls outside this tool.
Clean seven entries without merging local-part case
Inputs
Use the example containing Ada at an uppercase domain, a repeated Ada address, lowercase ada, Jane’s plus-tagged and dotted addresses, broken@ and ..dots@example.com. Keep the default duplicate comparison.
Result
Four addresses are kept, one duplicate is removed and two entries are flagged. Ada@example.com and ada@example.com remain separate. jane+news@example.org and jane.news@example.org are both retained.
What it means
Domain case is normalized, but local-part case and provider-specific aliases are not combined. The two flagged entries need review; this result is not a mailbox-existence test.
Common mistakes to avoid
Calling kept addresses verified
A syntactically supported address can still bounce or belong to someone else. Keep syntax cleaning separate from consent, mailbox verification and campaign permission.
Merging aliases indiscriminately
Dots and plus tags have provider-specific meanings. This cleaner retains them so it does not erase addresses based on a rule that may not apply.
Discarding unsupported addresses automatically
Some legitimate standards-compliant formats lie outside the supported subset. Use the audit to review those entries rather than treating every flagged address as impossible.
Frequently asked questions
Definitions, edge cases, and practical next steps for this tool. Search all tool FAQs ↗
Does this verify whether an email address exists?
No. It performs local syntax cleaning and duplicate comparison. It does not query DNS or MX records, open SMTP connections, send mail or inspect bounces. Mailbox existence, ownership and willingness to receive your message remain unknown.
Why is local-part case preserved by default?
The part before @ can have system-specific case behavior. The conservative default avoids merging Ada and ada automatically, while domains always ignore case. Choose whole-address case-insensitive comparison only when you understand and accept that additional merging.
Can I paste display names with addresses?
Yes, supported entries such as Ada <Ada@example.com> are extracted into an address. A name containing commas can be quoted, as in "Doe, Jane" <jane@example.org>. Newlines always separate entries; complex comments and quoted local parts need manual review.
Will Gmail dots or plus aliases be removed?
No. Dots and plus tags in the local part are retained. Provider-specific mailbox equivalence is beyond this cleaner, and the same transformation could change meaning on another domain. Normalize aliases only with a deliberate policy appropriate to the relevant provider.
Which address formats are flagged?
The supported subset uses common ASCII dot-atom local parts and dotted domains. Unicode addresses, quoted local parts, comments, domain literals and single-label domains are flagged for review. A flag can indicate unsupported syntax as well as a genuine mistake.
What is in the audit download?
The CSV includes each nonempty entry’s original text, cleaned address, status and explanation. Duplicate rows refer to the first matching entry. Keep the audit when you need to explain an import change or investigate why a contact was omitted.
Can this process my full contact CSV?
It does not map multiple CSV columns. Extract the email-address column into a newline-separated list first. Pasting names, IDs and other columns can produce misleading entries. You can use the CSV converter to inspect a file’s structure before preparing the address list.
Is a clean list ready to send a campaign?
Syntax cleaning is only one preparation step. Check your own subscription permission, suppression lists, unsubscribe state and source accuracy before importing. The tool supports up to 10,000 entries and keeps an audit, but it cannot decide who should receive your campaign.
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Sources and method
Use the references below to check definitions and platform guidance. The model’s scope and limits are explained above. Read our editorial standards.