mail-threading 0.1.3

JWZ email threading (RFC 5256). Reconstruct message threads from References/In-Reply-To headers, with subject fallback for broken clients.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43

{
  "name": "subject-prefixes-custom",
  "description": "Custom subject prefixes are honored by subject fallback.",
  "spec": {
    "source": "public API contract",
    "url": "https://www.jwz.org/doc/threading.html",
    "behavior": "subject prefix normalization is caller-configurable"
  },
  "options": {
    "subject_prefixes": [
      "respuesta"
    ]
  },
  "input": [
    {
      "id": "topic",
      "message_id": "<custom-prefix-topic@example>",
      "in_reply_to": null,
      "references": [],
      "subject": "Plan",
      "date": "2026-05-15T09:00:00Z"
    },
    {
      "id": "reply",
      "message_id": "<custom-prefix-reply@example>",
      "in_reply_to": null,
      "references": [],
      "subject": "Respuesta: Plan",
      "date": "2026-05-15T09:05:00Z"
    }
  ],
  "expected": {
    "threads": [
      {
        "root": "topic",
        "messages": [
          "topic",
          "reply"
        ]
      }
    ]
  }
}