# Email address list validate

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

Check RFC 5322 address-list syntax, including dots, quotes, comments, and groups.

**Use when you need to: validate an rfc 5322 address list · is this recipient list syntactically valid · reject consecutive dots in a mailbox domain.**

## Decide before calling

Read the [versioned contract](/v1/tools/email-address-list-validate/versions/1.0.0) and the supported scope below. Reuse `email-address-list-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-address-list-validate@1.0.0` for validate an rfc 5322 address list. 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 an rfc 5322 address list
- is this recipient list syntactically valid
- reject consecutive dots in a mailbox domain
- check group syntax in a recipient list
- find a bad local-part in an address list
- rfc 5322 address list syntax check

## Not supported

- return the mailbox tree
- rewrite the address list into canonical form
- check that the domain has an MX record

## Behavior

- Dot-atom-text is 1*atext *("." 1*atext) per RFC 5322 section 3.2.3, used by section 3.4.1. U+002E is not atext. A leading dot, a trailing dot, or two dots in a row is rejected in a local-part and in a domain, in both ascii and utf-8 modes. Inside a domain-literal or a quoted-string, a dot is ordinary text.
- mode ascii accepts only Unicode scalar values U+0000 through U+007F. mode utf-8 also treats U+0080 through U+10FFFF as atext, qtext, ctext, dtext and VCHAR, which is the RFC 6532 section 3.2 extension. The dot separator stays U+002E only.
- Well-typed text that is not a valid address-list returns valid false and a reason. Counts are zero in that case. Wrong types and limit breaches still throw.
- Obsolete null list slots and source routes (obs-route) are rejected. Domain-literals are not interpreted as IP addresses. RFC 5321 length limits and the SMTP requirement for a dot in the domain are not applied.
- The same text and mode always produce the same verdict. No clock, locale, or network.
- Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

## Input

- `text` (string, required): max length 2048
- `mode` (one of "ascii", "utf-8", required)

## Output

- `valid` (boolean, required)
- `reason` (one of "ok", "empty", "bad_local_part", "bad_domain", "invalid_address_list", "unbalanced_delimiter", "non_ascii", required)
- `address_count` (integer, required): min 0; max 32
- `mailbox_count` (integer, required): min 0; max 32
- `group_count` (integer, required): min 0; max 32

## Limits

- max input bytes: 2048
- max addresses: 32
- max groups: 32
- max comment depth: 8
- max output bytes: 65536

## Example

Request input:

```json
{
  "text": "Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>",
  "mode": "ascii"
}
```

Response:

```json
{
  "result": {
    "valid": true,
    "reason": "ok",
    "address_count": 3,
    "mailbox_count": 3,
    "group_count": 0
  }
}
```

## How to call it

### MCP

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

```json
{
  "id": "email-address-list-validate",
  "version": "1.0.0",
  "input": {
    "text": "Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>",
    "mode": "ascii"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/email-address-list-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"text":"Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>","mode":"ascii"}'
```

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

### CLI

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

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

## Related tools

- [Email mailbox validate](/tools/email-mailbox-validate): Check one RFC 5322 mailbox for syntax only and return a stable reason code.
- [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 parse](/tools/email-address-list-parse): Parse an RFC 5322 address-list into ordered mailboxes, groups, and a canonical form.
- [Email address list format](/tools/email-address-list-format): Format mailboxes and groups as one deterministic RFC 5322 address-list.
- [Email mailbox parse](/tools/email-mailbox-parse): Parse one RFC 5322 mailbox into parts and canonical text, without a delivery claim.
- [Email mailbox format](/tools/email-mailbox-format): Render a canonical RFC 5322 mailbox from decoded parts, without a delivery claim.