search: email address search + address-first ranking; inline images; folder i18n; link security

Search (PG backend):
- '@' terms match address substrings (from/to/cc), so a partial email like
  "dyrektor@wfdif" resolves and narrows predictably as you type
- index each address split into parts, so a bare domain/local word ("wfdif")
  finds the address (indexed as one lexeme otherwise); dotted terms fall back to
  an address substring
- rank sender/recipient name+address matches above body/subject-only ones
  (addr_hit tier, then recency); cursor extended to keep keyset pagination correct
- scripts/reindex_address_parts.py backfills address tokens into existing rows

Inline images:
- extract attachments via a full MIME walk instead of shallow iter_attachments(),
  which missed inline images nested in mixed>related>alternative (cid: rendered
  broken); has_attachments counts only real (non-cid) attachments
- scripts/backfill_inline_attachments.py stores previously-missed inline images

Folder-name i18n (SPEC §12 M2):
- accent/punctuation-insensitive, multi-delimiter (/ \ .) special-use inference
  across ~13 languages; curated names (no substring false positives)

Link security (reading panel):
- links never navigate the message iframe: a parent-side click interceptor opens
  http/https in a new tab (noopener) and mailto in the composer (recipient
  pre-filled); all other schemes blocked

Backend 292 tests green, ruff + mypy --strict clean; frontend tsc/eslint/vitest clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U72FZiF1W1pb8XxyWBTREA

backend/app/indexer/indexer.py

@@ -54,7 +54,7 @@ def _build_search_doc(message: Message, parsed: ParsedEmail, special_use: str |
         cc=parsed.cc_addr,
         subject=parsed.subject,
         body_text=parsed.text_body,
-        attachment_names=[a.filename for a in parsed.attachments],
+        attachment_names=[a.filename for a in parsed.attachments if a.content_id is None],
         has_attachments=parsed.has_attachments,
         is_unread="\\Seen" not in message.flags,
         is_starred="\\Flagged" in message.flags,

backend/app/indexer/mime.py

@@ -46,7 +46,9 @@ class ParsedEmail:
 
     @property
     def has_attachments(self) -> bool:
-        return len(self.attachments) > 0
+        # Inline resources (cid: images) carry a content_id and render in-body, not
+        # as attachment chips — only real attachments flip the paperclip.
+        return any(a.content_id is None for a in self.attachments)
 
     @property
     def snippet(self) -> str:
@@ -85,17 +87,25 @@ def _get_body_content(msg: EmailMessage, subtype: str) -> str | None:
 
 
 def _extract_attachments(msg: EmailMessage) -> list[ParsedAttachment]:
+    # Walk the whole tree, not iter_attachments(): the latter is shallow and treats
+    # multipart/related as a body, so an inline image nested in mixed>related>alt is
+    # never yielded (its cid: reference then renders broken). A part is an attachment
+    # or inline resource if it has a filename, a Content-ID, or attachment disposition;
+    # the body text/plain and text/html parts have none of these and are skipped.
     out: list[ParsedAttachment] = []
-    for part in msg.iter_attachments():
-        if not isinstance(part, EmailMessage):
+    for part in msg.walk():
+        if part.is_multipart() or not isinstance(part, EmailMessage):
+            continue
+        cid = part.get("Content-ID")
+        filename = part.get_filename()
+        if not (filename or cid or part.get_content_disposition() == "attachment"):
             continue
         payload = part.get_payload(decode=True)
         if not isinstance(payload, bytes):
             continue
-        cid = part.get("Content-ID")
         out.append(
             ParsedAttachment(
-                filename=part.get_filename() or "attachment",
+                filename=filename or "attachment",
                 mime_type=part.get_content_type(),
                 content_id=cid.strip("<>") if cid else None,
                 payload=payload,

backend/app/search/pg.py

@@ -15,7 +15,20 @@ import html
 import re
 from uuid import UUID
 
-from sqlalchemy import Text, any_, cast, exists, func, literal, not_, or_, select, tuple_, update
+from sqlalchemy import (
+    Text,
+    any_,
+    case,
+    cast,
+    exists,
+    func,
+    literal,
+    not_,
+    or_,
+    select,
+    tuple_,
+    update,
+)
 from sqlalchemy.sql.elements import ColumnElement
 
 from app.db import get_sessionmaker
@@ -42,12 +55,23 @@ def _prefix_tsquery(value: str) -> ColumnElement[object]:
 _RELATIVE_MULT = {"d": 1, "w": 7, "m": 30, "y": 365}
 
 
+def _email_parts(email: str) -> str:
+    """Split an address on @/./-/+/_ so its domain and local part are searchable
+    on their own — a bare "wfdif" should find dyrektor@wfdif.com.pl. Postgres
+    indexes the whole address as a single lexeme, so the parts are invisible to a
+    word search otherwise."""
+    return re.sub(r"[@._+\-]+", " ", email)
+
+
 def _doc_text_blob(doc: SearchDoc) -> str:
     parts = [doc.subject, doc.body_text]
     for field in (doc.from_, doc.to, doc.cc):
         for addr in field:
             parts.append(addr.get("name", ""))
-            parts.append(addr.get("email", ""))
+            email = addr.get("email", "")
+            if email:
+                parts.append(email)  # whole address (one lexeme, for exact/prefix)
+                parts.append(_email_parts(email))  # + its parts as separate tokens
     parts.extend(doc.attachment_names)
     return " ".join(p for p in parts if p)
 
@@ -114,7 +138,24 @@ class PgSearchBackend(SearchBackend):
             if clause.get("phrase"):
                 # Quoted phrase: keep exact-adjacency semantics, no prefix.
                 return Message.body_indexed.op("@@")(func.websearch_to_tsquery(_TS_CONFIG, value))
-            return Message.body_indexed.op("@@")(_prefix_tsquery(value))
+            like = f"%{value}%"
+            addr_match = or_(
+                cast(Message.from_addr, Text).ilike(like),
+                cast(Message.to_addr, Text).ilike(like),
+                cast(Message.cc_addr, Text).ilike(like),
+            )
+            if "@" in value:
+                # A term with '@' is an address search: match the address substring
+                # only (like from:/to:/cc:), so it narrows predictably as you type —
+                # not the split-word body matching that made a partial term over-hit.
+                return addr_match
+            fts = Message.body_indexed.op("@@")(_prefix_tsquery(value))
+            if "." in value:
+                # A dotted term (e.g. "wfdif.com") stays one host lexeme in FTS, so
+                # also match it as an address substring. Bare words don't need this:
+                # address parts are indexed as their own tokens (see _doc_text_blob).
+                return or_(fts, addr_match)
+            return fts
         key = clause.get("key")
         cond = self._filter_condition(str(key), value)
         return cond
@@ -189,7 +230,11 @@ class PgSearchBackend(SearchBackend):
         groups = q.filters.get("groups", []) if isinstance(q.filters, dict) else []
         assert isinstance(groups, list)
         conditions = self._build_conditions(groups)
+        terms = _positive_text_terms(groups)
 
+        # Rank a match in a sender/recipient name or address above a body/subject-only
+        # match, so "who" results come first; ties break by recency.
+        addr_hit = _address_hit_expr(terms)
         rank = (
             func.ts_rank_cd(Message.body_indexed, _prefix_tsquery(q.text))
             if q.text
@@ -203,6 +248,7 @@ class PgSearchBackend(SearchBackend):
                 Message.snippet,
                 Message.internal_date,
                 rank.label("score"),
+                addr_hit.label("addr_hit"),
             )
             .select_from(Message)
             .join(Mailbox, Mailbox.id == Message.mailbox_id)
@@ -213,14 +259,16 @@ class PgSearchBackend(SearchBackend):
 
         decoded = _decode_cursor(cursor)
         if decoded is not None:
-            cur_date, cur_id = decoded
+            cur_hit, cur_date, cur_id = decoded
+            # Keyset over the full ordering (addr_hit, date, id), all descending.
             stmt = stmt.where(
-                tuple_(Message.internal_date, Message.id)
-                < tuple_(literal(cur_date), literal(cur_id))
+                tuple_(addr_hit, Message.internal_date, Message.id)
+                < tuple_(literal(cur_hit), literal(cur_date), literal(cur_id))
             )
-        stmt = stmt.order_by(Message.internal_date.desc(), Message.id.desc()).limit(limit + 1)
+        stmt = stmt.order_by(
+            addr_hit.desc(), Message.internal_date.desc(), Message.id.desc()
+        ).limit(limit + 1)
 
-        terms = _positive_text_terms(groups)
         async with get_sessionmaker()() as session:
             rows = (await session.execute(stmt)).all()
 
@@ -236,7 +284,9 @@ class PgSearchBackend(SearchBackend):
             for row in rows
         ]
         next_cursor = (
-            _encode_cursor(rows[-1].internal_date, rows[-1].id) if has_more and rows else None
+            _encode_cursor(int(rows[-1].addr_hit), rows[-1].internal_date, rows[-1].id)
+            if has_more and rows
+            else None
         )
         return hits, next_cursor
 
@@ -250,6 +300,21 @@ def _positive_text_terms(groups: list[list[dict[str, object]]]) -> list[str]:
     return terms
 
 
+def _address_hit_expr(terms: list[str]) -> ColumnElement[int]:
+    """1 if any positive free-text term appears in a from/to/cc name or address,
+    else 0. Used to sort address/name matches ahead of body/subject-only ones."""
+    conds: list[ColumnElement[bool]] = []
+    for t in terms:
+        if t:
+            like = f"%{t}%"
+            conds.append(cast(Message.from_addr, Text).ilike(like))
+            conds.append(cast(Message.to_addr, Text).ilike(like))
+            conds.append(cast(Message.cc_addr, Text).ilike(like))
+    if not conds:
+        return literal(0)
+    return case((or_(*conds), 1), else_=0)
+
+
 def _highlights(subject: str, snippet: str, terms: list[str]) -> dict[str, str]:
     out: dict[str, str] = {}
     if not terms:
@@ -274,17 +339,17 @@ def _mark(value: str, terms: list[str]) -> str:
     return escaped
 
 
-def _encode_cursor(date: dt.datetime, message_id: UUID) -> str:
-    raw = f"{date.isoformat()}|{message_id}"
+def _encode_cursor(addr_hit: int, date: dt.datetime, message_id: UUID) -> str:
+    raw = f"{addr_hit}|{date.isoformat()}|{message_id}"
     return base64.urlsafe_b64encode(raw.encode()).decode()
 
 
-def _decode_cursor(cursor: str | None) -> tuple[dt.datetime, UUID] | None:
+def _decode_cursor(cursor: str | None) -> tuple[int, dt.datetime, UUID] | None:
     if not cursor:
         return None
     try:
         raw = base64.urlsafe_b64decode(cursor.encode()).decode()
-        date_str, id_str = raw.split("|", 1)
-        return dt.datetime.fromisoformat(date_str), UUID(id_str)
+        hit_str, date_str, id_str = raw.split("|", 2)
+        return int(hit_str), dt.datetime.fromisoformat(date_str), UUID(id_str)
     except (ValueError, TypeError):
         return None

backend/app/sync/folder_names.py

@@ -1,48 +1,120 @@
-"""Special-use inference from folder names (SPEC §6.3 fallback heuristics).
+"""Special-use inference from folder names (SPEC §6.3 / §12 M2 fallback).
 
-Used only when the server does not advertise SPECIAL-USE. Includes Polish names
-(Wysłane, Kosz, ...) alongside English/German, per the spec's i18n intent.
+Used only when the server does not advertise the SPECIAL-USE extension. Matching
+is accent- and punctuation-insensitive (so "Wysłane", "Éléments envoyés" and
+"Junk E-mail" all resolve), covers the hierarchy leaf under any of the common
+IMAP delimiters (``/  \\  .``), and recognises provider prefixes like
+``[Gmail]/`` implicitly via the leaf. Names are curated per language rather than
+substring-matched, so a folder like "Sent to John" is *not* misfiled as Sent.
 """
 
 from __future__ import annotations
 
+import unicodedata
+
+# Latin letters NFKD doesn't decompose to ASCII; fold them explicitly.
+_LATIN_SPECIAL = str.maketrans(
+    {"ł": "l", "ø": "o", "đ": "d", "ð": "d", "ß": "ss", "æ": "ae", "œ": "oe", "ı": "i", "þ": "th"}
+)
+
+
+def _compact(name: str) -> str:
+    """Fold to a comparable key: lowercase, strip accents/diacritics, drop every
+    non-alphanumeric char. "Éléments envoyés" -> "elementsenvoyes"."""
+    folded = unicodedata.normalize("NFKD", name.strip().lower()).translate(_LATIN_SPECIAL)
+    return "".join(ch for ch in folded if ch.isalnum())
+
+
+# Localized folder names by special_use. Written readably; compacted at load.
+_NAMES: dict[str, list[str]] = {
+    "sent": [
+        "sent", "sent items", "sent mail", "sent messages",  # English / Outlook / Gmail
+        "wysłane", "elementy wysłane", "wiadomości wysłane",  # Polish
+        "gesendet", "gesendete objekte", "gesendete elemente",  # German
+        "envoyés", "éléments envoyés", "messages envoyés", "courrier envoyé",  # French
+        "enviados", "elementos enviados", "correo enviado",  # Spanish
+        "inviata", "posta inviata", "messaggi inviati",  # Italian
+        "verzonden", "verzonden items", "verzonden berichten",  # Dutch
+        "enviadas", "itens enviados", "mensagens enviadas",  # Portuguese
+        "отправленные", "исходящие",  # Russian
+        "skickat", "skickade", "skickade objekt",  # Swedish
+        "sendt", "sendte", "sendte elementer",  # Norwegian / Danish
+        "lähetetyt",  # Finnish
+        "odeslané", "odeslaná pošta",  # Czech
+    ],
+    "drafts": [
+        "drafts", "draft",
+        "robocze", "kopie robocze", "wersje robocze",
+        "entwürfe", "entwurf",
+        "brouillons",
+        "borradores",
+        "bozze",
+        "concepten",
+        "rascunhos",
+        "черновики",
+        "utkast",
+        "kladder",  # Danish
+        "luonnokset",  # Finnish
+        "koncepty",  # Czech
+    ],
+    "trash": [
+        "trash", "deleted", "deleted items", "deleted messages", "bin", "recycle bin",
+        "kosz",
+        "papierkorb", "gelöschte objekte", "gelöschte elemente",
+        "corbeille", "éléments supprimés",
+        "papelera", "elementos eliminados",
+        "cestino", "posta eliminata",
+        "prullenbak", "verwijderde items",
+        "lixeira", "lixo", "itens excluídos",
+        "корзина", "удаленные",
+        "papperskorg", "borttaget",
+        "papirkurv", "slettet",
+        "roskakori", "poistetut",
+        "koš",  # Czech
+    ],
+    "junk": [
+        "junk", "junk email", "junk e-mail", "spam", "bulk mail", "bulk",
+        "wiadomości-śmieci", "niechciane",
+        "unerwünscht", "werbung",
+        "courrier indésirable", "indésirables", "pourriel",
+        "correo no deseado", "no deseado", "correo basura",
+        "posta indesiderata", "indesiderata",
+        "ongewenst", "ongewenste e-mail",
+        "lixo eletrônico",
+        "спам", "нежелательная почта",
+        "skräp", "skräppost",
+        "uønsket",
+        "roskaposti",
+        "nevyžádaná pošta",
+    ],
+    "archive": [
+        "archive", "archives", "all mail",
+        "archiwum",
+        "archiv",
+        "archivio",
+        "archivo",
+        "archief",
+        "arquivo", "arquivo morto",
+        "архив", "вся почта",
+        "arkiv",
+        "arkisto",
+    ],
+}
+
 _NAME_MAP: dict[str, str] = {
-    # sent
-    "sent": "sent",
-    "sent items": "sent",
-    "sent mail": "sent",
-    "wysłane": "sent",
-    "wyslane": "sent",
-    "elementy wysłane": "sent",
-    "gesendet": "sent",
-    # drafts
-    "drafts": "drafts",
-    "draft": "drafts",
-    "robocze": "drafts",
-    "kopie robocze": "drafts",
-    "entwürfe": "drafts",
-    # trash
-    "trash": "trash",
-    "deleted": "trash",
-    "deleted items": "trash",
-    "kosz": "trash",
-    "papierkorb": "trash",
-    # junk
-    "junk": "junk",
-    "spam": "junk",
-    "bulk mail": "junk",
-    "wiadomości-śmieci": "junk",
-    # archive
-    "archive": "archive",
-    "archiwum": "archive",
-    "all mail": "archive",
-    "archiv": "archive",
+    _compact(name): special for special, names in _NAMES.items() for name in names
 }
 
 
 def infer_special_use(path: str) -> str | None:
-    """Infer a special_use value from a mailbox path/name (case-insensitive)."""
-    if path.upper() == "INBOX":
+    """Infer a special_use value from a mailbox path/name (accent-insensitive)."""
+    if path.strip().upper().rstrip("/.") == "INBOX":
         return "inbox"
-    leaf = path.replace("\\", "/").split("/")[-1].strip().lower()
-    return _NAME_MAP.get(leaf) or _NAME_MAP.get(path.strip().lower())
+    # Take the hierarchy leaf under any common IMAP delimiter (/ \ or . for
+    # Dovecot/Courier namespaces), then fold for lookup.
+    normalized = path
+    for delim in ("/", "\\", "."):
+        normalized = normalized.replace(delim, "\n")
+    segments = [s for s in normalized.split("\n") if s.strip()]
+    tail = segments[-1] if segments else path
+    return _NAME_MAP.get(_compact(tail)) or _NAME_MAP.get(_compact(path))

backend/scripts/backfill_inline_attachments.py

@@ -0,0 +1,67 @@
+"""One-off: store inline (cid:) images that the old shallow attachment extractor
+missed for messages nested as mixed>related>alternative, so their cid: references
+resolve instead of rendering broken. Idempotent — skips content_ids already stored.
+
+Run: python -m scripts.backfill_inline_attachments
+"""
+
+from __future__ import annotations
+
+import asyncio
+
+from sqlalchemy import select
+
+from app.db import get_sessionmaker
+from app.indexer import blobstore
+from app.indexer.mime import parse_message
+from app.models import Attachment, Message
+
+
+async def main() -> None:
+    sm = get_sessionmaker()
+    added = 0
+    fixed_msgs = 0
+    async with sm() as session:
+        msgs = list(await session.scalars(select(Message)))
+        for msg in msgs:
+            try:
+                raw = blobstore.load(msg.user_id, msg.blob_sha256)
+            except FileNotFoundError:
+                continue
+            parsed = parse_message(raw)
+            inline = [a for a in parsed.attachments if a.content_id]
+            if not inline:
+                continue
+            have = set(
+                await session.scalars(
+                    select(Attachment.content_id).where(
+                        Attachment.message_id == msg.id, Attachment.content_id.is_not(None)
+                    )
+                )
+            )
+            new = 0
+            for att in inline:
+                if att.content_id in have:
+                    continue
+                att_sha = blobstore.store(msg.user_id, att.payload)
+                session.add(
+                    Attachment(
+                        message_id=msg.id,
+                        user_id=msg.user_id,
+                        filename=att.filename,
+                        mime_type=att.mime_type,
+                        size_bytes=len(att.payload),
+                        content_id=att.content_id,
+                        blob_sha256=att_sha,
+                    )
+                )
+                new += 1
+            if new:
+                added += new
+                fixed_msgs += 1
+        await session.commit()
+    print(f"stored {added} missing inline images across {fixed_msgs} messages")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

backend/scripts/reindex_address_parts.py

@@ -0,0 +1,56 @@
+"""One-off: add split-address tokens to existing messages' FTS vector.
+
+New messages get address parts indexed via `_doc_text_blob` (so a bare "wfdif"
+finds dyrektor@wfdif.com.pl). This backfills that into already-indexed rows by
+appending the split-address lexemes to `body_indexed`. Idempotent — tsvector
+concat merges duplicate lexemes, so re-running is harmless.
+
+Run: python -m scripts.reindex_address_parts
+"""
+
+from __future__ import annotations
+
+import asyncio
+
+from sqlalchemy import func, select, update
+
+from app.db import get_sessionmaker
+from app.models import Message
+from app.search.pg import _TS_CONFIG, _email_parts
+
+
+def _address_parts_blob(msg: Message) -> str:
+    parts: list[str] = []
+    for field in (msg.from_addr, msg.to_addr, msg.cc_addr):
+        for addr in field:
+            email = addr.get("email", "")
+            if email:
+                parts.append(_email_parts(email))
+    return " ".join(parts)
+
+
+async def main() -> None:
+    sm = get_sessionmaker()
+    updated = 0
+    async with sm() as session:
+        msgs = list(await session.scalars(select(Message).where(Message.body_indexed.is_not(None))))
+        for msg in msgs:
+            blob = _address_parts_blob(msg)
+            if not blob:
+                continue
+            await session.execute(
+                update(Message)
+                .where(Message.id == msg.id)
+                .values(
+                    body_indexed=Message.body_indexed.op("||")(
+                        func.to_tsvector(_TS_CONFIG, blob)
+                    )
+                )
+            )
+            updated += 1
+        await session.commit()
+    print(f"reindexed address parts into {updated} messages")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

backend/tests/indexer/test_mime.py

@@ -93,6 +93,39 @@ def test_attachment_extracted() -> None:
     assert parsed.attachments[0].payload == b"\x00\x01\x02data"
 
 
+def test_inline_image_nested_in_related_is_extracted() -> None:
+    # Real-world structure: mixed > related > alternative(text, html) + inline image.
+    # iter_attachments() misses the nested image; a full walk must find it so the
+    # cid: reference resolves (regression: broken inline image).
+    from email.mime.image import MIMEImage
+    from email.mime.multipart import MIMEMultipart
+    from email.mime.text import MIMEText
+
+    root = MIMEMultipart("mixed")
+    root["Subject"] = "newsletter"
+    root["From"] = "biuro@kipa.pl"
+    root["To"] = "me@example.com"
+    root["Message-ID"] = "<n@x.com>"
+    related = MIMEMultipart("related")
+    alt = MIMEMultipart("alternative")
+    alt.attach(MIMEText("text version", "plain"))
+    alt.attach(MIMEText('<p>Hi <img src="cid:img001"></p>', "html"))
+    related.attach(alt)
+    img = MIMEImage(b"\x89PNG\r\n\x1a\ndata", "png")
+    img.add_header("Content-ID", "<img001>")
+    img.add_header("Content-Disposition", "inline", filename="image001.png")
+    related.attach(img)
+    root.attach(related)
+
+    parsed = parse_message(root.as_bytes())
+    assert len(parsed.attachments) == 1
+    att = parsed.attachments[0]
+    assert att.content_id == "img001"
+    assert att.mime_type == "image/png"
+    # Inline-only: no attachment chip / paperclip.
+    assert parsed.has_attachments is False
+
+
 def test_missing_message_id_returns_none() -> None:
     msg = EmailMessage()
     msg["Subject"] = "no id"

backend/tests/search/test_search_api.py

@@ -168,6 +168,36 @@ async def test_free_text_full_email_address(seeded: Ctx) -> None:
     assert await _search(seeded, "bob@corp.co") == 1  # prefix while still typing
 
 
+async def test_free_text_email_matches_address_consistently(seeded: Ctx) -> None:
+    # A term with '@' is treated as an address search and matches as a substring
+    # of from/to/cc, so it narrows *predictably* as you type more of the address
+    # (a partial term never returns more than the fuller one).
+    assert await _search(seeded, "bob@") == 1  # local part -> bob only
+    assert await _search(seeded, "bob@corp") == 1
+    assert await _search(seeded, "bob@co") == 1
+    assert await _search(seeded, "@corp.com") == 3  # all three share the domain
+    assert await _search(seeded, "zzz@corp") == 0  # no such sender
+
+
+async def test_address_matches_rank_before_body_matches(ctx: Ctx) -> None:
+    # Older message matches "zebra" only via its sender address; the newer one
+    # matches only in the body. The address/name hit must still come first.
+    await _ingest(ctx, frm="Zebra Corp <hello@zebra.com>", subject="hi", body="nothing here")
+    await _ingest(ctx, frm="Someone <someone@corp.com>", subject="a note", body="the zebra ran")
+    resp = await ctx.client.get("/api/search", params={"q": "zebra"})
+    subjects = [t["thread"]["subject"] for t in resp.json()["threads"]]
+    assert subjects == ["hi", "a note"]  # address hit first, then body-only
+
+
+async def test_free_text_bare_domain_word_matches_address(seeded: Ctx) -> None:
+    # A bare domain/local word finds the address even though Postgres indexes the
+    # whole address as one lexeme — address parts are tokenized at index time.
+    assert await _search(seeded, "corp") == 3  # the domain word -> all three
+    assert await _search(seeded, "carol") == 1  # local part -> carol only
+    # A dotted domain term also matches via the address-substring fallback.
+    assert await _search(seeded, "corp.com") == 3
+
+
 async def test_from_operator(seeded: Ctx) -> None:
     assert await _search(seeded, "from:bob") == 1
     assert await _search(seeded, "from:corp.com") == 3  # all three share the domain

backend/tests/sync/test_folder_names.py

@@ -1,4 +1,4 @@
-"""Folder-name special-use heuristics (SPEC §6.3)."""
+"""Folder-name special-use heuristics (SPEC §6.3 / §12 M2)."""
 
 from __future__ import annotations
 
@@ -10,24 +10,64 @@ from app.sync.folder_names import infer_special_use
 @pytest.mark.parametrize(
     "path,expected",
     [
+        # inbox
         ("INBOX", "inbox"),
         ("inbox", "inbox"),
+        ("INBOX.", "inbox"),  # Dovecot may show a trailing delimiter
+        # English / Outlook / Gmail
         ("Sent", "sent"),
-        ("Wysłane", "sent"),  # Polish
-        ("Elementy wysłane", "sent"),
-        ("Gesendet", "sent"),  # German
+        ("Sent Items", "sent"),
+        ("[Gmail]/Sent Mail", "sent"),
         ("Drafts", "drafts"),
-        ("Robocze", "drafts"),
-        ("Trash", "trash"),
-        ("Kosz", "trash"),  # Polish
-        ("Papierkorb", "trash"),  # German
-        ("Spam", "junk"),
+        ("Deleted Items", "trash"),
+        ("Bin", "trash"),
         ("Junk", "junk"),
+        ("Junk E-mail", "junk"),  # Outlook, punctuation-insensitive
+        ("[Gmail]/Spam", "junk"),
         ("Archive", "archive"),
+        ("[Gmail]/All Mail", "archive"),
+        # Polish (accents)
+        ("Wysłane", "sent"),
+        ("Elementy wysłane", "sent"),
+        ("Robocze", "drafts"),
+        ("Kosz", "trash"),
+        ("Wiadomości-śmieci", "junk"),
         ("Archiwum", "archive"),
-        ("INBOX/Sent", "sent"),  # nested leaf
+        # German
+        ("Gesendet", "sent"),
+        ("Gesendete Elemente", "sent"),
+        ("Entwürfe", "drafts"),
+        ("Papierkorb", "trash"),
+        ("Gelöschte Elemente", "trash"),
+        # French
+        ("Éléments envoyés", "sent"),
+        ("Brouillons", "drafts"),
+        ("Corbeille", "trash"),
+        ("Courrier indésirable", "junk"),
+        # Spanish / Italian / Dutch / Portuguese
+        ("Enviados", "sent"),
+        ("Papelera", "trash"),
+        ("Posta inviata", "sent"),
+        ("Cestino", "trash"),
+        ("Verzonden", "sent"),
+        ("Prullenbak", "trash"),
+        ("Itens enviados", "sent"),
+        ("Lixeira", "trash"),
+        # Russian (Cyrillic)
+        ("Отправленные", "sent"),
+        ("Корзина", "trash"),
+        ("Черновики", "drafts"),
+        ("Спам", "junk"),
+        # delimiters / nesting
+        ("INBOX/Sent", "sent"),
+        ("INBOX.Sent", "sent"),  # Dovecot dot delimiter
+        ("INBOX.Trash", "trash"),
+        # negatives — must not misfire
         ("Work", None),
         ("Random Folder", None),
+        ("Sent to John", None),  # curated names, not substring match
+        ("Newsletter", None),
+        ("Projects/Client", None),
     ],
 )
 def test_infer_special_use(path: str, expected: str | None) -> None:

frontend/src/components/thread/MessageBody.tsx

@@ -12,7 +12,13 @@ import { Attachments } from "./Attachments";
 // measure the content to auto-size the frame — so the message shows in full and
 // only the thread panel scrolls — and (b) send the session cookie so inline
 // (cid:) images authenticate and load.
-export function MessageBody({ message }: { message: MessageEnvelope }) {
+export function MessageBody({
+  message,
+  onMailto,
+}: {
+  message: MessageEnvelope;
+  onMailto?: (email: string) => void;
+}) {
   const t = useT();
   const queryClient = useQueryClient();
   // Seed from the server's trusted-sender flag so an already-approved sender
@@ -20,6 +26,8 @@ export function MessageBody({ message }: { message: MessageEnvelope }) {
   const [allowed, setAllowed] = useState(message.images_allowed);
   const frameRef = useRef<HTMLIFrameElement>(null);
   const observerRef = useRef<ResizeObserver | null>(null);
+  const onMailtoRef = useRef(onMailto);
+  onMailtoRef.current = onMailto;
   const [height, setHeight] = useState(80);
 
   const { data, isLoading, isError } = useQuery({
@@ -73,11 +81,31 @@ export function MessageBody({ message }: { message: MessageEnvelope }) {
     [resize],
   );
 
+  // Links must NEVER navigate the message iframe (security: a click would replace
+  // the message body, and could be used for clickjacking/phishing). The frame is
+  // same-origin, so the parent intercepts clicks here: http/https open in a new
+  // tab (noopener), mailto opens the composer, and every other scheme is blocked.
+  const handleFrameClick = useCallback((e: Event) => {
+    const el = e.target as Element | null;
+    const anchor = el?.closest?.("a[href]") as HTMLAnchorElement | null;
+    if (!anchor) return;
+    const raw = (anchor.getAttribute("href") || "").trim();
+    e.preventDefault();
+    if (/^mailto:/i.test(raw)) {
+      const email = decodeURIComponent(raw.replace(/^mailto:/i, "").split("?")[0]).trim();
+      if (email) onMailtoRef.current?.(email);
+    } else if (/^https?:\/\//i.test(raw)) {
+      window.open(anchor.href, "_blank", "noopener,noreferrer");
+    }
+    // else: relative / cid: / javascript: / data: / tel: — blocked, no navigation.
+  }, []);
+
   const onLoad = () => {
     const doc = frameRef.current?.contentDocument;
     if (!doc) return;
     injectQuoteToggle(doc);
     resize();
+    doc.addEventListener("click", handleFrameClick);
     // Re-measure as images finish loading (they change the content height).
     doc.querySelectorAll("img").forEach((img) => {
       if (!img.complete) img.addEventListener("load", resize, { once: true });

frontend/src/components/thread/ThreadView.tsx

@@ -218,6 +218,7 @@ function MessageItem({
   alsoIn,
   onToggle,
   onReply,
+  onMailto,
   onToggleRead,
   onPrint,
   onDelete,
@@ -235,6 +236,7 @@ function MessageItem({
   alsoIn: string[];
   onToggle: () => void;
   onReply: (kind: string) => void;
+  onMailto: (email: string) => void;
   onToggleRead: () => void;
   onPrint: () => void;
   onDelete: () => void;
@@ -385,7 +387,7 @@ function MessageItem({
             </div>
           </div>
           <div className="px-4 pb-3">
-            <MessageBody message={message} />
+            <MessageBody message={message} onMailto={onMailto} />
           </div>
           {showReplyBar && canReply && (
             <div className="flex gap-2 border-t border-app-border px-4 py-3">
@@ -479,6 +481,16 @@ export function ThreadView({
     setComposing({ anchorId: msg.id, init: buildReplyInit(subject, msg, kind) });
   };
 
+  // A mailto: link in the message body opens a fresh composer to that address,
+  // sent from the account this message belongs to.
+  const openMailto = (msg: MessageEnvelope, email: string) => {
+    setExpanded((prev) => new Set(prev).add(msg.id));
+    setComposing({
+      anchorId: msg.id,
+      init: { accountId: msg.account_id, kind: "new", to: email, subject: "" },
+    });
+  };
+
   useEffect(() => {
     if (replyKindSignal && newest) openReply(newest, replyKindSignal.kind);
     // eslint-disable-next-line react-hooks/exhaustive-deps
@@ -583,6 +595,7 @@ export function ThreadView({
                 alsoIn={alsoIn}
                 onToggle={() => toggle(message.id)}
                 onReply={(kind) => openReply(message, kind)}
+                onMailto={(email) => openMailto(message, email)}
                 onToggleRead={() => toggleRead(message)}
                 onPrint={() => void printMessages(subject, [message])}
                 onDelete={() => deleteMessage(message)}