Email address normalize

email-address-normalize · version 1.0.0 · Communications · free, no key needed

Validate one email addr-spec and return its canonical form: minimal quoting, NFC local-part, lowercase domain.

Use when you need to: normalize an email address · canonical form of an email address · lowercase the domain of an email address.

Decide before calling

Read the versioned contract and the supported scope below. Reuse email-address-normalize@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use email-address-normalize@1.0.0 for normalize an email address. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• normalize an email address
• canonical form of an email address
• lowercase the domain of an email address
• remove unnecessary quotes from an email local part
• are these two email addresses the same mailbox
• validate email address syntax strictly
• נרמול כתובת אימייל

Not supported

• lowercase the local-part or strip dots and +tags (provider-specific, not standard)
• convert internationalized domains between U-labels and A-labels (IDNA)
• parse "Name <addr>" display-name forms, comments or domain literals
• check deliverability with DNS, MX or SMTP

Behavior

• Accepts exactly one addr-spec: a dot-atom or RFC 5321 Quoted-string local-part (no FWS, no HTAB), "@", and a domain of at least two ASCII LDH labels; non-ASCII local-part characters must be Unicode letters, marks or numbers (RFC 6531 3.3 subset).
• The quoted form is decoded (each quoted-pair stands for its character, RFC 5322 3.2.1), NFC-normalized (RFC 6532 3.1), then written with minimum quoting (RFC 5321 4.1.2): unquoted when it is valid dot-atom text, otherwise quoted with only "\" and DQUOTE escaped.
• Local-part case is preserved (RFC 5321 2.4: local-parts are case sensitive); the domain is ASCII-lowercased (domains are not case sensitive). No provider-specific rules are applied.
• Limits: local-part at most 64 octets (as written and as normalized), labels at most 63, address at most 254 (RFC 5321 4.5.3.1); the top-level label must not be all-numeric (RFC 3696 2).
• invalid_input (details.reason) for syntax errors; unsupported_input for well-formed features outside the subset: comments or surrounding white space, display names, domain literals, single-label or U-label domains, obsolete local-parts, non-letter non-ASCII characters.
• requires_smtputf8 is true when the normalized address contains non-ASCII characters (RFC 6531). changed is true when the normalized address differs from the input. Unicode classes and NFC come from the runtime Unicode version.
• An address longer than 254 UTF-8 bytes is limit_exceeded, checked before parsing.

Input

• address (string, required): min length 1; One addr-spec, at most 254 UTF-8 bytes, no surrounding white space.

Output

• address (string, required): min length 5; max length 254
• local_part (string, required): min length 1; max length 64
• domain (string, required): min length 3; max length 252
• local_part_form (one of "dot-atom", "quoted-string", required)
• requires_smtputf8 (boolean, required)
• changed (boolean, required)

Limits

• max address bytes: 254

Example

Request input:

{
  "address": "\"john.q.public\"@Example.COM"
}

Response:

{
  "result": {
    "address": "john.q.public@example.com",
    "local_part": "john.q.public",
    "domain": "example.com",
    "local_part_form": "dot-atom",
    "requires_smtputf8": false,
    "changed": true
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "email-address-normalize",
  "version": "1.0.0",
  "input": {
    "address": "\"john.q.public\"@Example.COM"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/email-address-normalize/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"address":"\"john.q.public\"@Example.COM"}'

The machine-readable contract is at /v1/tools/email-address-normalize/versions/1.0.0.

CLI

node cli.mjs run email-address-normalize 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Email address list deduplicate: Drop duplicate mailboxes in an RFC 5322 address-list, keeping the first one.
• Email address list validate: Check RFC 5322 address-list syntax, including dots, quotes, comments, and groups.
• Email address list parse: Parse an RFC 5322 address-list into ordered mailboxes, groups, and a canonical form.
• Email mailbox format: Render a canonical RFC 5322 mailbox from decoded parts, without a delivery claim.
• Email address list format: Format mailboxes and groups as one deterministic RFC 5322 address-list.
• Email mailbox parse: Parse one RFC 5322 mailbox into parts and canonical text, without a delivery claim.