# Email mailbox validate

`email-mailbox-validate` · version 1.0.0 · Communications · free, no key needed

Check one RFC 5322 mailbox for syntax only and return a stable reason code.

**Use when you need to: validate rfc 5322 mailbox syntax · check one mailbox grammar only · mailbox syntax reason without dns.**

## Decide before calling

Read the [versioned contract](/v1/tools/email-mailbox-validate/versions/1.0.0) and the supported scope below. Reuse `email-mailbox-validate@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-mailbox-validate@1.0.0` for validate rfc 5322 mailbox syntax. 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

- validate rfc 5322 mailbox syntax
- check one mailbox grammar only
- mailbox syntax reason without dns
- reject obsolete mailbox phrase dots
- is this single mailbox syntactically valid
- detect unclosed mailbox quotes
- בדיקת תחביר של תיבת דואר

## Not supported

- return the display-name word list
- claim the address exists or can receive mail
- validate SPF DKIM or DMARC
- validate a comma-separated address list

## Behavior

- Well-typed mailbox text that fails RFC 5322 syntax returns {valid:false, reason}. It does not throw. Wrong types, unknown fields, lone surrogates, and declared limits throw. The grammar matches email-mailbox-parse: phrase words, dot-atom, quoted-string, comments, and domain-literals; obsolete dots in a display name are invalid_display_name.
- A valid result returns form and canonical text using the same canonical quoting as the parser. utf8 defaults to false. true selects RFC 6532 UTF-8 scalars without normalization. No DNS lookup and no deliverability claim.
- reason is one of: non_ascii, invalid_local_part, invalid_domain, invalid_domain_literal, invalid_display_name, invalid_quoted_string, invalid_comment, obsolete_route, not_a_single_mailbox, unclosed_quote, unclosed_comment, unclosed_domain_literal, unclosed_angle, invalid_quoted_pair, trailing_junk.

## Input

- `mailbox` (string, required): min length 1; max length 256
- `utf8` (boolean, optional)

## Output

- `valid` (boolean, required)
- `reason` (one of "non_ascii", "invalid_local_part", "invalid_domain", "invalid_domain_literal", "invalid_display_name", "invalid_quoted_string", "invalid_comment", "obsolete_route", "not_a_single_mailbox", "unclosed_quote", "unclosed_comment", "unclosed_domain_literal", "unclosed_angle", "invalid_quoted_pair", "trailing_junk", optional)
- `form` (one of "addr-spec", "name-addr", optional)
- `canonical` (string, optional): min length 3; max length 1600

## Limits

- max mailbox bytes: 256
- max local part chars: 64
- max domain chars: 190
- max display words: 8
- max word chars: 64
- max comment depth: 4
- max comments: 8
- max output bytes: 2048

## Example

Request input:

```json
{
  "mailbox": "Who? <one@y.test>"
}
```

Response:

```json
{
  "result": {
    "valid": true,
    "form": "name-addr",
    "canonical": "Who? <one@y.test>"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "email-mailbox-validate",
  "version": "1.0.0",
  "input": {
    "mailbox": "Who? <one@y.test>"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/email-mailbox-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"mailbox":"Who? <one@y.test>"}'
```

The machine-readable contract is at [/v1/tools/email-mailbox-validate/versions/1.0.0](/v1/tools/email-mailbox-validate/versions/1.0.0).

### CLI

```sh
node cli.mjs run email-mailbox-validate 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

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