diff --git a/backend/app/api/messages.py b/backend/app/api/messages.py
index ab25826..357340b 100644
--- a/backend/app/api/messages.py
+++ b/backend/app/api/messages.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import asyncio
 import html as html_lib
 import io
 import uuid
@@ -19,10 +20,11 @@ from app.api.schemas import AttachmentOut
 from app.api.settings import add_allowed_image_sender, allowed_image_senders
 from app.db import get_session
 from app.identity.deps import CurrentUser, require_csrf
-from app.indexer import blobstore
+from app.indexer import blobstore, thumbs
 from app.indexer.mime import parse_message
 from app.indexer.sanitize import SANITIZER_VERSION, sanitize_html
-from app.models import Attachment, BodyPart, Message
+from app.indexer.thumbs import thumb_type
+from app.models import Attachment, BodyPart, ComposeAttachment, Message
 
 router = APIRouter(prefix="/messages", tags=["mail"])
 
@@ -190,6 +192,37 @@ async def list_attachments(
     ]
 
 
+@router.post(
+    "/{message_id}/forward-attachments",
+    response_model=list[AttachmentOut],
+    dependencies=[Depends(require_csrf)],
+)
+async def forward_attachments(
+    message_id: uuid.UUID, user: CurrentUser, db: DbSession
+) -> list[AttachmentOut]:
+    """Attach a message's files to a forward of it: one compose attachment per
+    real (non-inline) attachment, sharing the stored blob — nothing is copied.
+    Returns them as the composer lists its attachments."""
+    await _owned_message(db, user.id, message_id)
+    rows = [
+        ComposeAttachment(
+            user_id=user.id,
+            filename=a.filename,
+            mime_type=a.mime_type,
+            size_bytes=a.size_bytes,
+            blob_sha256=a.blob_sha256,
+        )
+        for a in await _real_attachments(db, message_id)
+        if blobstore.exists(user.id, a.blob_sha256)
+    ]
+    db.add_all(rows)
+    await db.commit()
+    return [
+        AttachmentOut(id=r.id, filename=r.filename, mime_type=r.mime_type, size_bytes=r.size_bytes)
+        for r in rows
+    ]
+
+
 @router.get("/{message_id}/attachments.zip")
 async def download_attachments_zip(
     message_id: uuid.UUID,
@@ -232,6 +265,33 @@ async def download_attachments_zip(
     )
 
 
+@router.get("/{message_id}/attachments/{attachment_id}/thumb")
+async def attachment_thumbnail(
+    message_id: uuid.UUID, attachment_id: uuid.UUID, user: CurrentUser, db: DbSession
+) -> Response:
+    """A small preview of an image or a PDF's first page (WebP, at most
+    480 px, aspect kept). 404 when the file cannot have one: the reading pane
+    then shows its type icon instead."""
+    msg = await _owned_message(db, user.id, message_id)
+    att = await db.scalar(
+        select(Attachment).where(
+            Attachment.id == attachment_id, Attachment.message_id == message_id
+        )
+    )
+    kind = thumb_type(att.mime_type, att.filename) if att is not None else None
+    if att is None or kind is None:
+        raise_api_error(404, "not_found", "no thumbnail")
+    data = await asyncio.to_thread(thumbs.thumbnail, msg.user_id, att.blob_sha256, kind)
+    if data is None:
+        raise_api_error(404, "not_found", "no thumbnail")
+    # An attachment never changes under its id: the browser may keep this.
+    return Response(
+        content=data,
+        media_type="image/webp",
+        headers={"Cache-Control": "private, max-age=31536000, immutable"},
+    )
+
+
 @router.get("/{message_id}/attachments/{attachment_id}")
 async def message_attachment(
     message_id: uuid.UUID,
diff --git a/backend/app/indexer/thumbs.py b/backend/app/indexer/thumbs.py
new file mode 100644
index 0000000..0758e31
--- /dev/null
+++ b/backend/app/indexer/thumbs.py
@@ -0,0 +1,115 @@
+"""Attachment thumbnails for the reading pane: images and a PDF's first page.
+
+A thumbnail fits within THUMB_MAX × THUMB_MAX with its aspect ratio kept (the
+browser decides how to frame it), as WebP. Made once and kept beside the blob
+store — ``{BLOB_ROOT}/{user}/thumbs/{sha}-{THUMB_MAX}.webp`` — with a ``.none``
+marker for files that cannot have one (a broken image, an encrypted PDF, HEIC),
+so neither is attempted twice.
+
+Attachments are hostile input: decoding runs in a worker thread, oversized
+files and decompression bombs are refused.
+"""
+
+from __future__ import annotations
+
+import io
+import logging
+import uuid
+from pathlib import Path
+
+from app.indexer import blobstore
+
+logger = logging.getLogger(__name__)
+
+THUMB_MAX = 480  # px: sharp on a 2× screen for a tile of up to 230 px
+_MAX_INPUT_BYTES = 40 * 1024 * 1024
+_MAX_PIXELS = 64_000_000  # a larger image is refused, not decoded
+_IMAGE_MIME = frozenset(
+    {"image/jpeg", "image/png", "image/gif", "image/webp", "image/bmp", "image/tiff"}
+)
+
+
+_EXT_MIME = {
+    "jpg": "image/jpeg",
+    "jpeg": "image/jpeg",
+    "png": "image/png",
+    "gif": "image/gif",
+    "webp": "image/webp",
+    "bmp": "image/bmp",
+    "tif": "image/tiff",
+    "tiff": "image/tiff",
+    "pdf": "application/pdf",
+}
+
+
+def thumb_type(mime_type: str, filename: str) -> str | None:
+    """The type to render a thumbnail as, or None. Senders often label files
+    application/octet-stream, so the extension stands in for a missing type."""
+    mime = mime_type.lower()
+    if mime in _IMAGE_MIME or mime == "application/pdf":
+        return mime
+    return _EXT_MIME.get(filename.rsplit(".", 1)[-1].lower()) if "." in filename else None
+
+
+def can_thumbnail(mime_type: str) -> bool:
+    return mime_type in _IMAGE_MIME or mime_type == "application/pdf"
+
+
+def _path(user_id: uuid.UUID, sha: str, suffix: str) -> Path:
+    return blobstore.blob_path(user_id, sha).parent.parent / "thumbs" / f"{sha}-{THUMB_MAX}{suffix}"
+
+
+def _render(data: bytes, mime_type: str) -> bytes | None:
+    from PIL import Image, ImageOps
+
+    Image.MAX_IMAGE_PIXELS = _MAX_PIXELS  # beyond: DecompressionBombError
+    if mime_type == "application/pdf":
+        import pypdfium2 as pdfium  # type: ignore[import-untyped]
+
+        doc = pdfium.PdfDocument(data)
+        try:
+            page = doc[0]
+            width, height = page.get_size()
+            scale = THUMB_MAX / max(width, height, 1)
+            img = page.render(scale=scale, draw_annots=True).to_pil()
+        finally:
+            doc.close()
+    else:
+        img = Image.open(io.BytesIO(data))
+        img.seek(0)  # an animation: its first frame
+        img = ImageOps.exif_transpose(img)  # phone photos: upright
+        img.thumbnail((THUMB_MAX, THUMB_MAX))
+    if img.mode not in ("RGB", "RGBA"):
+        img = img.convert("RGBA" if "A" in img.getbands() or img.mode == "P" else "RGB")
+    out = io.BytesIO()
+    img.save(out, "WEBP", quality=80, method=4)
+    return out.getvalue()
+
+
+def thumbnail(user_id: uuid.UUID, sha: str, mime_type: str) -> bytes | None:
+    """The thumbnail of a stored attachment, or None if it cannot have one.
+
+    Blocking (decoding is CPU work): call it in a thread.
+    """
+    done = _path(user_id, sha, ".webp")
+    if done.exists():
+        return done.read_bytes()
+    none = _path(user_id, sha, ".none")
+    if none.exists() or not can_thumbnail(mime_type):
+        return None
+    path = blobstore.blob_path(user_id, sha)
+    if not path.exists() or path.stat().st_size > _MAX_INPUT_BYTES:
+        return None
+    try:
+        thumb = _render(path.read_bytes(), mime_type)
+    except Exception as exc:  # noqa: BLE001 - any undecodable file: no thumbnail
+        logger.info("no thumbnail for blob %s (%s): %s", sha, mime_type, exc)
+        thumb = None
+    done.parent.mkdir(parents=True, exist_ok=True)
+    if thumb is None:
+        none.touch()
+        return None
+    tmp = done.with_suffix(".tmp")
+    tmp.write_bytes(thumb)
+    tmp.replace(done)
+    return thumb
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index e820bec..eeb72ed 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -36,6 +36,11 @@ dependencies = [
     # DEPENDENCY: autoconfig/ISPDB return XML from untrusted servers; defusedxml
     # blocks XXE/billion-laughs that stdlib ElementTree is vulnerable to (§10 hostile input).
     "defusedxml~=0.7",
+    # DEPENDENCY: thumbnails of attachments in the reading pane — Pillow scales
+    # images; pypdfium2 renders a PDF's first page (a self-contained wheel, no
+    # system libraries, so the slim runtime image needs nothing extra).
+    "pillow~=11.0",
+    "pypdfium2~=4.30",
 ]
 
 [project.optional-dependencies]
diff --git a/backend/tests/api/test_api.py b/backend/tests/api/test_api.py
index 609d829..f84588c 100644
--- a/backend/tests/api/test_api.py
+++ b/backend/tests/api/test_api.py
@@ -475,3 +475,133 @@ async def test_thread_pagination_offset(api: ApiCtx) -> None:
     assert len(body2["threads"]) == 1
     assert body2["total"] == body["total"]  # grand total is stable across pages
     assert body2["threads"][0]["id"] != body["threads"][0]["id"]
+
+
+async def test_forward_carries_the_attachments(api: ApiCtx) -> None:
+    # Forwarding attaches the original's files (not its inline images), sharing
+    # the stored blob — and sending the forward then really includes them.
+    from app.indexer import blobstore
+    from app.models import Attachment, ComposeAttachment, Draft
+    from app.outbox.attachments import load_attachments
+
+    assert api.session is not None
+    mid = api.message_ids[-1]
+    sha = blobstore.store(api.user_id, b"%PDF-1.4 quarterly numbers")
+    logo = blobstore.store(api.user_id, b"\x89PNG logo")
+    api.session.add_all(
+        [
+            Attachment(
+                message_id=mid,
+                user_id=api.user_id,
+                filename="numbers.pdf",
+                mime_type="application/pdf",
+                size_bytes=26,
+                content_id=None,
+                blob_sha256=sha,
+            ),
+            Attachment(
+                message_id=mid,
+                user_id=api.user_id,
+                filename="logo.png",
+                mime_type="image/png",
+                size_bytes=9,
+                content_id="logo@x",  # inline: part of the body, not a file
+                blob_sha256=logo,
+            ),
+        ]
+    )
+    await api.session.commit()
+
+    api.client.cookies.set("csrf", "t")  # a POST: double-submit CSRF
+    resp = await api.client.post(
+        f"/api/messages/{mid}/forward-attachments", headers={"X-CSRF": "t"}
+    )
+    assert resp.status_code == 200
+    body = resp.json()
+    assert [(a["filename"], a["size_bytes"]) for a in body] == [("numbers.pdf", 26)]
+    row = await api.session.get(ComposeAttachment, uuid.UUID(body[0]["id"]))
+    assert row is not None and row.blob_sha256 == sha and row.user_id == api.user_id
+
+    draft = Draft(
+        user_id=api.user_id,
+        account_id=api.account_id,
+        kind="forward",
+        payload={
+            "to": ["bob@example.com"],
+            "subject": "Fwd: Lunch",
+            "attachment_ids": [body[0]["id"]],
+        },
+    )
+    assert await load_attachments(api.session, api.user_id, draft) == [
+        ("numbers.pdf", "application/pdf", b"%PDF-1.4 quarterly numbers")
+    ]
+
+    # Someone else's message: not found.
+    other = await api.client.post(
+        f"/api/messages/{uuid.uuid4()}/forward-attachments", headers={"X-CSRF": "t"}
+    )
+    assert other.status_code == 404
+
+
+async def test_attachment_thumbnails(api: ApiCtx) -> None:
+    # Images and a PDF's first page get a WebP preview (aspect kept, at most
+    # 480 px, browser-cacheable); other files, and broken ones, get a 404.
+    import io
+
+    import pypdfium2 as pdfium  # type: ignore[import-untyped]
+    from PIL import Image
+
+    from app.indexer import blobstore
+    from app.models import Attachment
+
+    assert api.session is not None
+    mid = api.message_ids[-1]
+
+    def png(w: int, h: int) -> bytes:
+        out = io.BytesIO()
+        Image.new("RGB", (w, h), (200, 30, 30)).save(out, "PNG")
+        return out.getvalue()
+
+    pdf = pdfium.PdfDocument.new()
+    pdf.new_page(595, 842)
+    pdf_bytes = io.BytesIO()
+    pdf.save(pdf_bytes)
+
+    files = {
+        "wide.png": ("image/png", png(1600, 400)),
+        "scan.pdf": ("application/octet-stream", pdf_bytes.getvalue()),  # mislabelled
+        "notes.txt": ("text/plain", b"hello"),
+        "broken.jpg": ("image/jpeg", b"not really a jpeg"),
+    }
+    ids: dict[str, uuid.UUID] = {}
+    for name, (mime, data) in files.items():
+        att = Attachment(
+            message_id=mid,
+            user_id=api.user_id,
+            filename=name,
+            mime_type=mime,
+            size_bytes=len(data),
+            content_id=None,
+            blob_sha256=blobstore.store(api.user_id, data),
+        )
+        api.session.add(att)
+        await api.session.flush()
+        ids[name] = att.id
+    await api.session.commit()
+
+    def url(name: str) -> str:
+        return f"/api/messages/{mid}/attachments/{ids[name]}/thumb"
+
+    wide = await api.client.get(url("wide.png"))
+    assert wide.status_code == 200 and wide.headers["content-type"] == "image/webp"
+    assert "immutable" in wide.headers["cache-control"]
+    assert Image.open(io.BytesIO(wide.content)).size == (480, 120)  # aspect kept
+    assert (await api.client.get(url("wide.png"))).content == wide.content  # cached
+
+    page = await api.client.get(url("scan.pdf"))
+    assert page.status_code == 200
+    w, h = Image.open(io.BytesIO(page.content)).size
+    assert h == 480 and 330 < w < 350  # an A4 page, upright
+
+    assert (await api.client.get(url("notes.txt"))).status_code == 404
+    assert (await api.client.get(url("broken.jpg"))).status_code == 404
diff --git a/frontend/public/sw.js b/frontend/public/sw.js
index a4839db..6bd968d 100644
--- a/frontend/public/sw.js
+++ b/frontend/public/sw.js
@@ -51,7 +51,9 @@ const META = new Set([
 ]);
 const ID = "[0-9a-fA-F-]{36}";
 const THREAD_RE = new RegExp(`^/api/threads/(${ID})$`);
-const MESSAGE_RE = new RegExp(`^/api/messages/(${ID})/(?:html|attachments|cid/.+)$`);
+const MESSAGE_RE = new RegExp(
+  `^/api/messages/(${ID})/(?:html|attachments|attachments/${ID}/thumb|cid/.+)$`,
+);
 const ID_IN_PATH = new RegExp(ID);
 const PLUGIN_UI_RE = /^\/api\/plugins\/[^/]+\/ui\//; // plugin bundles (Labels' sidebar…)
 
diff --git a/frontend/src/components/Switch.tsx b/frontend/src/components/Switch.tsx
new file mode 100644
index 0000000..d43cbd6
--- /dev/null
+++ b/frontend/src/components/Switch.tsx
@@ -0,0 +1,39 @@
+// An on/off switch: off shows a dark knob with ✕ on a grey track, on a light
+// knob with ✓ on the accent colour.
+export function Switch({
+  checked,
+  onChange,
+  label,
+  disabled = false,
+}: {
+  checked: boolean;
+  onChange: (value: boolean) => void;
+  /** Accessible name, when no visible <label> points at the switch. */
+  label?: string;
+  disabled?: boolean;
+}) {
+  return (
+    <button
+      type="button"
+      role="switch"
+      aria-checked={checked}
+      aria-label={label}
+      disabled={disabled}
+      onClick={() => onChange(!checked)}
+      className={`relative h-6 w-11 shrink-0 rounded-full border transition-colors disabled:opacity-50 ${
+        checked ? "border-app-accent bg-app-accent" : "border-app-border bg-app-hover"
+      }`}
+    >
+      <span
+        aria-hidden
+        className={`absolute top-1/2 flex h-[18px] w-[18px] -translate-y-1/2 items-center justify-center rounded-full transition-all ${
+          checked ? "left-[21px] bg-white text-app-accent" : "left-[2px] bg-app-fg text-app-bg"
+        }`}
+      >
+        <svg width="10" height="10" viewBox="0 0 10 10" fill="none" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round">
+          {checked ? <path d="M2 5.2l2 2 4-4.4" /> : <path d="M2.8 2.8l4.4 4.4M7.2 2.8l-4.4 4.4" />}
+        </svg>
+      </span>
+    </button>
+  );
+}
diff --git a/frontend/src/components/compose/Composer.tsx b/frontend/src/components/compose/Composer.tsx
index f3bc916..60c1f34 100644
--- a/frontend/src/components/compose/Composer.tsx
+++ b/frontend/src/components/compose/Composer.tsx
@@ -40,6 +40,8 @@ export interface ComposerInit {
   // A reply/forward quotes the original: this attribution line sits above the
   // quoted message body (fetched from the original message's sanitized HTML).
   quote?: { attribution: string; messageId: string };
+  // A forward: the message whose attachments go along with it.
+  forwardFrom?: string;
   // A message kept on this device (written offline; lib/scheduled.ts).
   localId?: string;
   localState?: LocalState; // "scheduled" when reopened from Scheduled
@@ -336,6 +338,25 @@ export function Composer({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []);
 
+  // A forward carries the original's attachments (shared on the server, not
+  // re-uploaded). Once per window: StrictMode runs effects twice in dev, so a
+  // ref — not a cancel flag — keeps it from attaching them twice.
+  const forwardedFrom = useRef(false);
+  useEffect(() => {
+    const source = init.forwardFrom;
+    if (!source || init.draftId || forwardedFrom.current) return;
+    forwardedFrom.current = true;
+    void api
+      .forwardAttachments(source)
+      .then((rows) => {
+        if (rows.length) setAttachments((prev) => [...rows, ...prev]);
+      })
+      .catch((e) => {
+        if (!isOfflineError(e)) setAttachError(t("compose.forwardAttachFailed"));
+      });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
   const addFiles = async (files: FileList | File[]) => {
     markDirty();
     setAttachError("");
diff --git a/frontend/src/components/list/MessageList.tsx b/frontend/src/components/list/MessageList.tsx
index 628ca96..a576586 100644
--- a/frontend/src/components/list/MessageList.tsx
+++ b/frontend/src/components/list/MessageList.tsx
@@ -4,6 +4,7 @@ import { useEffect, useRef } from "react";
 
 import { useT } from "../../i18n";
 import { api } from "../../lib/api";
+import { useListDividers } from "../../lib/listDividers";
 import { useSavedThreads } from "../../lib/offline";
 import { formatClock, getDateLocale } from "../../lib/timeFormat";
 import type { Address, ThreadSummary } from "../../lib/types";
@@ -140,6 +141,8 @@ export function MessageList({
   const labelMap = labelsQuery.data ?? {};
   // Offline: conversations not saved on this device are shown faded.
   const saved = useSavedThreads();
+  // Optional thin line between rows (Mailbox display).
+  const dividers = useListDividers();
 
   // The user's own addresses, shown as "me" in the sender column.
   const accounts = useQuery({ queryKey: ["accounts"], queryFn: api.accounts });
@@ -212,6 +215,15 @@ export function MessageList({
                 dimmed ? "pointer-events-none opacity-40" : "cursor-pointer"
               } ${unsaved ? "opacity-45" : ""}`}
             >
+              {dividers && item.index > 0 && (
+                // Midway through the gap above the row, lined up with its content.
+                <div
+                  aria-hidden
+                  className={`pointer-events-none absolute inset-x-5 h-px bg-app-border ${
+                    compact ? "top-2.5" : "top-[3px]"
+                  }`}
+                />
+              )}
               <div
                 className={`flex h-full items-center gap-3 rounded-lg px-3 ${
                   selected || checked ? "bg-app-active" : "group-hover:bg-app-hover"
diff --git a/frontend/src/components/mail/ListDividersOption.tsx b/frontend/src/components/mail/ListDividersOption.tsx
new file mode 100644
index 0000000..400415f
--- /dev/null
+++ b/frontend/src/components/mail/ListDividersOption.tsx
@@ -0,0 +1,16 @@
+import { useT } from "../../i18n";
+import { setListDividers, useListDividers } from "../../lib/listDividers";
+import { Switch } from "../Switch";
+
+/** "Show a dividing line between rows" — under the layout choice, in the ⋯
+ *  menu's Mailbox display and in Settings → Appearance. Applies at once. */
+export function ListDividersOption() {
+  const t = useT();
+  const on = useListDividers();
+  return (
+    <label className="flex cursor-pointer items-center justify-between gap-3 text-[14px] text-app-fg">
+      <span>{t("display.dividers")}</span>
+      <Switch checked={on} onChange={setListDividers} label={t("display.dividers")} />
+    </label>
+  );
+}
diff --git a/frontend/src/components/mail/MailboxDisplay.tsx b/frontend/src/components/mail/MailboxDisplay.tsx
index d5f51e3..6fb6ef0 100644
--- a/frontend/src/components/mail/MailboxDisplay.tsx
+++ b/frontend/src/components/mail/MailboxDisplay.tsx
@@ -1,12 +1,14 @@
 import { useEffect, useRef } from "react";
 
 import { useT } from "../../i18n";
+import { ListDividersOption } from "./ListDividersOption";
 import { ReadingPanePicker } from "./ReadingPanePicker";
 
 /**
- * "Mailbox display": the reading-pane choice, opened from the list's ⋯ menu.
- * Anchored below that menu. Picking a layout applies it and closes the popover;
- * ✕, Escape or a click elsewhere closes it without a change.
+ * "Mailbox display": the reading-pane choice and the row dividers, opened from
+ * the list's ⋯ menu. Anchored below that menu. Picking a layout applies it and
+ * closes the popover; the dividers switch applies at once and leaves it open;
+ * ✕, Escape or a click elsewhere closes it.
  */
 export function MailboxDisplay({ onClose }: { onClose: () => void }) {
   const t = useT();
@@ -48,6 +50,9 @@ export function MailboxDisplay({ onClose }: { onClose: () => void }) {
       </div>
       <p className="mb-2 text-[13px] font-medium text-app-fg">{t("display.readingPane")}</p>
       <ReadingPanePicker onPick={onClose} />
+      <div className="mt-4 border-t border-app-border pt-3">
+        <ListDividersOption />
+      </div>
     </div>
   );
 }
diff --git a/frontend/src/components/thread/Attachments.tsx b/frontend/src/components/thread/Attachments.tsx
index 7b0b81b..877dd2f 100644
--- a/frontend/src/components/thread/Attachments.tsx
+++ b/frontend/src/components/thread/Attachments.tsx
@@ -113,6 +113,172 @@ function DownloadGlyph() {
   );
 }
 
+// --- tiles ---------------------------------------------------------------------
+
+// Every tile is the same size: at most 230 px wide, and narrower when the
+// reading column is, so at least three still fit in a row (gap-2: 2 × 8 px).
+const TILE_WIDTH = "min(230px, calc((100% - 16px) / 3))";
+const TILE_RATIO = 230 / 146;
+
+const THUMB_EXT = new Set(["jpg", "jpeg", "png", "gif", "webp", "bmp", "tif", "tiff", "pdf"]);
+
+/** How a thumbnail sits in its tile, decided once it has loaded. */
+type Fit =
+  | "loading"
+  | "cover" // close to the tile's shape: fill it, trimming a little
+  | "whole" // very tall / wide / square-ish: all of it, over a blurred copy
+  | "small" // smaller than the tile: as is, not blown up
+  | "page" // a PDF: the top of its first page, like a document
+  | "none"; // no thumbnail: the type icon instead
+
+function fitFor(img: HTMLImageElement, pdf: boolean, tileWidth: number): Fit {
+  if (pdf) return "page";
+  const w = img.naturalWidth;
+  const h = img.naturalHeight;
+  if (!w || !h) return "none";
+  // The server keeps the original size when it is smaller than its 480 px
+  // limit: smaller than the tile itself means a small picture (an icon, a logo).
+  if (w < tileWidth && h < tileWidth / TILE_RATIO) return "small";
+  const ratio = w / h;
+  return ratio >= TILE_RATIO / 1.5 && ratio <= TILE_RATIO * 1.5 ? "cover" : "whole";
+}
+
+function AttachmentTile({
+  messageId,
+  att,
+  checked,
+  onToggle,
+  onOpen,
+}: {
+  messageId: string;
+  att: AttachmentOut;
+  checked: boolean;
+  onToggle: () => void;
+  /** Open the in-app preview; absent for types it cannot show (they download). */
+  onOpen?: () => void;
+}) {
+  const t = useT();
+  const ext = extOf(att.filename);
+  const pdf = ext === "pdf";
+  const [fit, setFit] = useState<Fit>(THUMB_EXT.has(ext) ? "loading" : "none");
+  const thumb = fit !== "none";
+  const src = api.attachmentThumbUrl(messageId, att.id);
+  const download = api.attachmentDownloadUrl(messageId, att.id);
+
+  const open = () => {
+    if (onOpen) onOpen();
+    else window.location.href = download;
+  };
+
+  return (
+    <div
+      role="button"
+      tabIndex={0}
+      aria-label={att.filename}
+      title={att.filename}
+      onClick={open}
+      onKeyDown={(e) => {
+        if (e.key === "Enter" || e.key === " ") {
+          e.preventDefault();
+          open();
+        }
+      }}
+      style={{ width: TILE_WIDTH, aspectRatio: `${TILE_RATIO}` }}
+      className={`wm-tile group/tile relative cursor-pointer overflow-hidden rounded-lg border bg-app-surface focus:outline-none focus-visible:ring-2 focus-visible:ring-app-accent ${
+        checked ? "border-app-accent ring-1 ring-app-accent" : "border-app-border"
+      }`}
+    >
+      {thumb ? (
+        <div className={`absolute inset-0 ${pdf ? "bg-white" : "bg-app-hover"}`}>
+          {fit === "whole" && (
+            // The same picture, blurred, filling the space beside it.
+            <img
+              src={src}
+              alt=""
+              aria-hidden
+              className="absolute inset-0 h-full w-full scale-110 object-cover opacity-60 blur-lg"
+            />
+          )}
+          <img
+            src={src}
+            alt=""
+            loading="lazy"
+            draggable={false}
+            onLoad={(e) => {
+              const tile = e.currentTarget.closest<HTMLElement>("[role=button]");
+              setFit(fitFor(e.currentTarget, pdf, tile?.clientWidth ?? 230));
+            }}
+            onError={() => setFit("none")}
+            className={`relative h-full w-full transition-opacity ${
+              fit === "loading" ? "opacity-0" : "opacity-100"
+            } ${
+              fit === "cover"
+                ? "object-cover"
+                : fit === "page"
+                  ? "object-cover object-top"
+                  : fit === "small"
+                    ? "object-scale-down"
+                    : "object-contain"
+            }`}
+          />
+        </div>
+      ) : (
+        // No picture: the file type, large, above the name bar.
+        <div className="wm-tile-art absolute inset-x-0 top-0 bottom-[46px] flex items-center justify-center bg-app-hover/60 [&_svg]:h-11 [&_svg]:w-11">
+          <AttachmentIcon filename={att.filename} />
+        </div>
+      )}
+
+      {/* Name bar: over a picture it shows on hover (or when ticked / focused);
+          a tile without one always shows it. */}
+      <div
+        className={`wm-tile-bar absolute inset-x-0 bottom-0 flex h-[46px] items-center gap-2 px-2.5 transition-opacity ${
+          thumb
+            ? `bg-black/70 text-white backdrop-blur-sm ${
+                checked ? "opacity-100" : "opacity-0 group-hover/tile:opacity-100 group-focus-within/tile:opacity-100"
+              }`
+            : "border-t border-app-border bg-app-surface text-app-fg"
+        }`}
+      >
+        <input
+          type="checkbox"
+          checked={checked}
+          onChange={onToggle}
+          onClick={(e) => e.stopPropagation()}
+          className="h-3.5 w-3.5 shrink-0 accent-app-accent"
+          aria-label={att.filename}
+        />
+        <span className="wm-tile-icon shrink-0 [&_svg]:h-5 [&_svg]:w-5">
+          <AttachmentIcon filename={att.filename} />
+        </span>
+        <span className="min-w-0 flex-1 leading-tight">
+          <span
+            className={`block truncate text-[13px] font-medium ${
+              onOpen ? (thumb ? "text-sky-300" : "text-app-accent") : ""
+            }`}
+          >
+            {att.filename}
+          </span>
+          <span className={`wm-tile-size block text-[11px] ${thumb ? "text-white/70" : "text-app-faint"}`}>
+            {formatSize(att.size_bytes)}
+          </span>
+        </span>
+        <a
+          href={download}
+          onClick={(e) => e.stopPropagation()}
+          title={t("mail.download")}
+          aria-label={`${t("mail.download")} ${att.filename}`}
+          className={`shrink-0 rounded p-1 ${
+            thumb ? "text-white/80 hover:bg-white/15 hover:text-white" : "text-app-muted hover:bg-app-hover hover:text-app-fg"
+          }`}
+        >
+          <DownloadGlyph />
+        </a>
+      </div>
+    </div>
+  );
+}
+
 export function Attachments({ messageId }: { messageId: string }) {
   const t = useT();
   const [selected, setSelected] = useState<Set<string>>(new Set());
@@ -158,44 +324,14 @@ export function Attachments({ messageId }: { messageId: string }) {
       )}
       <div className="flex flex-wrap gap-2">
         {attachments.map((att: AttachmentOut) => (
-          <div
+          <AttachmentTile
             key={att.id}
-            className="flex min-w-[13rem] max-w-[18rem] items-center gap-2 rounded-md border border-app-border bg-app-surface px-2.5 py-2"
-          >
-            <input
-              type="checkbox"
-              checked={selected.has(att.id)}
-              onChange={() => toggle(att.id)}
-              className="h-3.5 w-3.5 shrink-0 accent-app-accent"
-              aria-label={att.filename}
-            />
-            <AttachmentIcon filename={att.filename} />
-            <span className="min-w-0 flex-1">
-              {isPreviewable(att.filename) ? (
-                <button
-                  type="button"
-                  onClick={() => openPreview(att.id)}
-                  title={att.filename}
-                  className="block w-full truncate text-left text-sm font-medium text-app-accent hover:underline"
-                >
-                  {att.filename}
-                </button>
-              ) : (
-                <span className="block truncate text-sm font-medium text-app-fg" title={att.filename}>
-                  {att.filename}
-                </span>
-              )}
-              <span className="block text-xs text-app-faint">{formatSize(att.size_bytes)}</span>
-            </span>
-            <a
-              href={api.attachmentDownloadUrl(messageId, att.id)}
-              title={t("mail.download")}
-              aria-label={`${t("mail.download")} ${att.filename}`}
-              className="shrink-0 rounded p-1.5 text-app-muted hover:bg-app-hover hover:text-app-fg"
-            >
-              <DownloadGlyph />
-            </a>
-          </div>
+            messageId={messageId}
+            att={att}
+            checked={selected.has(att.id)}
+            onToggle={() => toggle(att.id)}
+            onOpen={isPreviewable(att.filename) ? () => openPreview(att.id) : undefined}
+          />
         ))}
       </div>
       <div className="mt-2">
diff --git a/frontend/src/components/thread/ThreadView.tsx b/frontend/src/components/thread/ThreadView.tsx
index 6bf55d2..662b4e2 100644
--- a/frontend/src/components/thread/ThreadView.tsx
+++ b/frontend/src/components/thread/ThreadView.tsx
@@ -72,6 +72,7 @@ function buildReplyInit(subject: string, msg: MessageEnvelope, kind: string): Co
       kind,
       subject: `Fwd: ${norm}`,
       quote,
+      forwardFrom: msg.id,
     };
   }
   const to = kind === "reply_all" ? [from, ...toEmails].filter(Boolean).join(", ") : from;
diff --git a/frontend/src/i18n/en.ts b/frontend/src/i18n/en.ts
index 830d6d4..2b95dc3 100644
--- a/frontend/src/i18n/en.ts
+++ b/frontend/src/i18n/en.ts
@@ -362,7 +362,7 @@ export const en = {
   "settings.spellcheck": "Spelling and grammar check",
   "settings.on": "On",
   "settings.off": "Off",
-  "settings.spellcheckLanguage": "Language",
+  "settings.spellcheckLanguage": "Spellchecking language",
   "settings.spellcheckAuto": "Auto-detect (each paragraph)",
   "settings.spellcheckUnavailable": "Not available: this server has no spell-checking engine set up.",
   "settings.recoveryEmailHint":
@@ -484,7 +484,7 @@ export const en = {
   "display.side": "Side",
   "display.bottom": "Bottom",
   "display.off": "Off",
-  "display.phoneNote": "On a phone, mail always opens in a single panel.",
+  "display.dividers": "Show a dividing line between rows",
   "admin.mail": "Outgoing system mail",
   "admin.mailHelp":
     "The mail account the server sends password-reset links from. Without it, “Forgot password?” sends nothing.",
@@ -561,6 +561,7 @@ export const en = {
   "offline.draftsNotSaved": "Only drafts written on this device are available offline.",
   "compose.sendLater": "Schedule",
   "compose.savedOnDevice": "Saved on this device",
+  "compose.forwardAttachFailed": "Couldn't attach the original message's files.",
   "compose.attachOnDevice": "On this device — uploaded when you're back online",
   "compose.onDevice": "On this device",
   "nav.scheduled": "Scheduled",
diff --git a/frontend/src/index.css b/frontend/src/index.css
index d39f4b2..e9c07ea 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -245,3 +245,29 @@ html[data-offline] .wm-online-only:hover {
     transform: translate(-50%, 0);
   }
 }
+
+/* Attachment tiles (thread/Attachments.tsx) shrink with the reading column so
+   three fit in a row; their name bar adapts to the tile's own width. */
+.wm-tile {
+  container-type: inline-size;
+}
+@container (max-width: 160px) {
+  .wm-tile-icon,
+  .wm-tile-size {
+    display: none;
+  }
+  .wm-tile-bar {
+    height: 34px;
+    gap: 6px;
+    padding-inline: 6px;
+  }
+}
+@container (max-width: 80px) {
+  /* Too small for a name: the picture (or icon) alone; a click still opens it. */
+  .wm-tile-bar {
+    display: none;
+  }
+  .wm-tile-art {
+    bottom: 0;
+  }
+}
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index 9f44026..bdc2a24 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -191,6 +191,9 @@ export const api = {
   },
 
   messageHtmlUrl: (id: string) => `/api/messages/${id}/html`,
+  // A forward's attachments: the original's files, as compose attachments.
+  forwardAttachments: (id: string) =>
+    apiFetch<AttachmentOut[]>(`/messages/${id}/forward-attachments`, { method: "POST" }),
 
   // --- account wizard ---
   discover: (email: string) =>
@@ -411,6 +414,9 @@ export const api = {
   // --- attachments ---
   messageAttachments: (messageId: string) =>
     apiFetch<AttachmentOut[]>(`/messages/${messageId}/attachments`),
+  // A small preview (images, a PDF's first page); 404 when there is none.
+  attachmentThumbUrl: (messageId: string, attachmentId: string) =>
+    `/api/messages/${messageId}/attachments/${attachmentId}/thumb`,
   attachmentDownloadUrl: (messageId: string, attachmentId: string) =>
     `/api/messages/${messageId}/attachments/${attachmentId}?download=1`,
   // Inline URL (no ?download): safe types are served with their real content-type
diff --git a/frontend/src/lib/listDividers.ts b/frontend/src/lib/listDividers.ts
new file mode 100644
index 0000000..dfaa46d
--- /dev/null
+++ b/frontend/src/lib/listDividers.ts
@@ -0,0 +1,39 @@
+// Whether the mail list draws a thin line between its rows (Mailbox display /
+// Settings → Appearance). Off by default; per device, in localStorage, like the
+// reading-pane layout it sits under.
+
+import { useSyncExternalStore } from "react";
+
+const KEY = "mail.listDividers";
+const EVENT = "webmail:list-dividers";
+
+function read(): boolean {
+  try {
+    return localStorage.getItem(KEY) === "1";
+  } catch {
+    return false;
+  }
+}
+
+function subscribe(onChange: () => void): () => void {
+  // Our own writes (same tab) and other tabs' writes (the storage event).
+  window.addEventListener(EVENT, onChange);
+  window.addEventListener("storage", onChange);
+  return () => {
+    window.removeEventListener(EVENT, onChange);
+    window.removeEventListener("storage", onChange);
+  };
+}
+
+export function useListDividers(): boolean {
+  return useSyncExternalStore(subscribe, read, () => false);
+}
+
+export function setListDividers(on: boolean): void {
+  try {
+    localStorage.setItem(KEY, on ? "1" : "0");
+  } catch {
+    /* private mode: the choice simply does not stick */
+  }
+  window.dispatchEvent(new Event(EVENT));
+}
diff --git a/frontend/src/routes/settings/Settings.tsx b/frontend/src/routes/settings/Settings.tsx
index 4c62249..581b5b9 100644
--- a/frontend/src/routes/settings/Settings.tsx
+++ b/frontend/src/routes/settings/Settings.tsx
@@ -5,6 +5,7 @@ import { Link, useLocation, useNavigate, useParams, useSearchParams } from "reac
 
 import { RichTextEditor } from "../../components/compose/RichTextEditor";
 import { TypedPasswordInput } from "../../components/TypedPasswordInput";
+import { ListDividersOption } from "../../components/mail/ListDividersOption";
 import { ReadingPanePicker } from "../../components/mail/ReadingPanePicker";
 import { useT } from "../../i18n";
 import { api, ApiError } from "../../lib/api";
@@ -926,8 +927,9 @@ function AppearanceSection() {
         <div className="max-w-md">
           <ReadingPanePicker />
         </div>
-        {/* Saved per device, like the theme: the right choice depends on the screen. */}
-        <p className="text-xs text-app-faint">{t("display.phoneNote")}</p>
+        <div className="max-w-md pt-2">
+          <ListDividersOption />
+        </div>
       </div>
       <SpellcheckSetting />
       <label className="flex items-center justify-between border-b border-app-border py-2 text-sm">