Email address list deduplicate

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

Drop duplicate mailboxes in an RFC 5322 address-list, keeping the first one.

Use when you need to: deduplicate an rfc 5322 address list · remove duplicate mailboxes and keep the first · unique addr-spec list that preserves groups.

Decide before calling

Read the versioned contract and the supported scope below. Reuse email-address-list-deduplicate@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-deduplicate@1.0.0 for deduplicate 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

• deduplicate an rfc 5322 address list
• remove duplicate mailboxes and keep the first
• unique addr-spec list that preserves groups
• collapse repeated recipients in a to header
• dedupe an address list by local-part and domain
• first occurrence mailbox deduplication

Not supported

• fold the local-part to lowercase
• parse a CSV of recipients
• merge two headers that are not already one address-list

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.
• Two mailboxes match when their decoded local-parts are identical and, for a dot-atom domain, their ASCII A-Z letters fold to lowercase. Domain-literals do not fold. The first display name wins. Order is the order of first occurrence.
• Members are deduped inside each group. A later group whose canonical text matches an earlier group is dropped. A mailbox inside a group does not collide with a top-level mailbox.
• 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 remove the same mailboxes. No clock, locale, or network.
• Disclaimer: format transform only; provides no confidentiality, integrity, or authenticity.

Input

• text (string, required): min length 1; max length 2048
• mode (one of "ascii", "utf-8", required)

Output

• mode (one of "ascii", "utf-8", required)
• canonical (string, required): min length 1; max length 8192
• address_count (integer, required): min 1; max 32
• mailbox_count (integer, required): min 0; max 32
• group_count (integer, required): min 0; max 32
• input_mailbox_count (integer, required): min 0; max 32
• removed_count (integer, required): min 0; max 32
• addresses (array of object or object, required): min items 1; max items 32

Limits

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

Example

Request input:

{
  "text": "A@Ex.COM, A@ex.com, a@ex.com",
  "mode": "ascii"
}

Response:

{
  "result": {
    "mode": "ascii",
    "canonical": "A@Ex.COM, a@ex.com",
    "address_count": 2,
    "mailbox_count": 2,
    "group_count": 0,
    "input_mailbox_count": 3,
    "removed_count": 1,
    "addresses": [
      {
        "kind": "mailbox",
        "display_name": "",
        "local_part": "A",
        "domain": "Ex.COM",
        "addr_spec": "A@Ex.COM"
      },
      {
        "kind": "mailbox",
        "display_name": "",
        "local_part": "a",
        "domain": "ex.com",
        "addr_spec": "a@ex.com"
      }
    ]
  }
}

How to call it

MCP

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

{
  "id": "email-address-list-deduplicate",
  "version": "1.0.0",
  "input": {
    "text": "A@Ex.COM, A@ex.com, a@ex.com",
    "mode": "ascii"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/email-address-list-deduplicate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"text":"A@Ex.COM, A@ex.com, a@ex.com","mode":"ascii"}'

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

CLI

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

Get the client at /clients/cli/.

Related tools

• Email address list parse: Parse an RFC 5322 address-list into ordered mailboxes, groups, and a canonical form.
• Email address list format: Format mailboxes and groups as one deterministic RFC 5322 address-list.
• Email address list validate: Check RFC 5322 address-list syntax, including dots, quotes, comments, and groups.
• Email mailbox parse: Parse one RFC 5322 mailbox into parts and canonical text, without a delivery claim.
• Email mailbox format: Render a canonical RFC 5322 mailbox from decoded parts, without a delivery claim.
• Email mailbox validate: Check one RFC 5322 mailbox for syntax only and return a stable reason code.