diff --git a/components/email/email-composer.tsx b/components/email/email-composer.tsx
index 9df87f82..523b58c9 100644
--- a/components/email/email-composer.tsx
+++ b/components/email/email-composer.tsx
@@ -11,6 +11,7 @@ import { debug } from "@/lib/debug";
 import { toast } from "@/stores/toast-store";
 import { sanitizeSignatureHtml, sanitizeEmailHtml } from "@/lib/email-sanitization";
 import { buildReplySubject, buildForwardSubject } from "@/lib/subject-prefix";
+import { isFilePreviewable } from "@/lib/file-preview";
 import { buildQuotedHtmlBlock, serializeEditorContent } from "@/components/email/quoted-html";
 import { emailHooks, contactHooks } from "@/lib/plugin-hooks";
 import type { OutgoingEmail, RecipientSuggestion } from "@/lib/plugin-types";
@@ -25,6 +26,7 @@ import { buildMimeMessage, wrapCmsAsSmimeMessage } from "@/lib/smime/mime-builde
 import type { MimeAttachment } from "@/lib/smime/mime-builder";
 import { smimeSign } from "@/lib/smime/smime-sign";
 import { PluginSlot } from "@/components/plugins/plugin-slot";
+import { FilePreviewModal } from "@/components/files/file-preview-modal";
 import { smimeEncrypt } from "@/lib/smime/smime-encrypt";
 import { useContactStore } from "@/stores/contact-store";
 import { useTemplateStore } from "@/stores/template-store";
@@ -452,6 +454,7 @@ export function EmailComposer({
   const [showSaveAsTemplate, setShowSaveAsTemplate] = useState(false);
   const [showCloseDialog, setShowCloseDialog] = useState(false);
   const [showAllAttachments, setShowAllAttachments] = useState(false);
+  const [previewAttachment, setPreviewAttachment] = useState<ComposerAttachment | null>(null);
   const [smimeSign_, setSmimeSign] = useState(false);
   const [smimeEncrypt_, setSmimeEncrypt] = useState(false);
   const [smimePassphrasePrompt, setSmimePassphrasePrompt] = useState<{ keyId: string; resolve: (passphrase: string) => void; reject: () => void } | null>(null);
@@ -1123,6 +1126,43 @@ export function EmailComposer({
     setAttachments(prev => prev.filter((_, i) => i !== index));
   };
 
+  // Inline preview for composer attachments, reusing the message viewer's
+  // FilePreviewModal (so previewability and the open-in-new-tab safety gate are
+  // handled there). Prefer the local File - no network - and fall back to the
+  // uploaded blob (forwarded attachments, which carry only a blobId).
+  const getPreviewAttachmentContent = useCallback(async () => {
+    if (!previewAttachment) throw new Error('No attachment selected');
+    if (previewAttachment.file) {
+      return {
+        blob: previewAttachment.file,
+        contentType: previewAttachment.type || previewAttachment.file.type || 'application/octet-stream',
+      };
+    }
+    if (composerClient && previewAttachment.blobId) {
+      const blob = await composerClient.fetchBlob(previewAttachment.blobId, previewAttachment.name, previewAttachment.type);
+      return { blob, contentType: previewAttachment.type || blob.type || 'application/octet-stream' };
+    }
+    throw new Error('No attachment content available');
+  }, [previewAttachment, composerClient]);
+
+  const handlePreviewAttachmentDownload = useCallback(async () => {
+    if (!previewAttachment) return;
+    if (previewAttachment.file) {
+      const url = URL.createObjectURL(previewAttachment.file);
+      const a = document.createElement('a');
+      a.href = url;
+      a.download = previewAttachment.name;
+      document.body.appendChild(a);
+      a.click();
+      document.body.removeChild(a);
+      URL.revokeObjectURL(url);
+      return;
+    }
+    if (composerClient && previewAttachment.blobId) {
+      await composerClient.downloadBlob(previewAttachment.blobId, previewAttachment.name, previewAttachment.type);
+    }
+  }, [previewAttachment, composerClient]);
+
   // Auto-save draft functionality
   const saveDraftOnce = async (): Promise<string | null> => {
     if (!client || !composerClient) return null;
@@ -2207,7 +2247,21 @@ export function EmailComposer({
         {attachments.length > 0 && (
           <div className="px-4 py-2 border-t shrink-0">
             <div className="flex flex-wrap gap-2">
-              {(showAllAttachments ? attachments : attachments.slice(0, 3)).map((att, index) => (
+              {(showAllAttachments ? attachments : attachments.slice(0, 3)).map((att, index) => {
+                // Clickable to preview only once it has content (local File or an
+                // uploaded blob) and the type is previewable; never mid-upload.
+                const canPreview = !att.uploading && !att.error
+                  && (!!att.file || !!att.blobId)
+                  && isFilePreviewable(att.name, att.type);
+                const label = (
+                  <>
+                    <span className="max-w-[150px] md:max-w-[200px] truncate">{att.name}</span>
+                    <span className="text-xs text-muted-foreground whitespace-nowrap">
+                      ({formatFileSize(att.size)})
+                    </span>
+                  </>
+                );
+                return (
                 <div
                   key={index}
                   className={cn(
@@ -2229,10 +2283,18 @@ export function EmailComposer({
                     ) : (
                       <Paperclip className="w-3 h-3 flex-shrink-0" />
                     )}
-                    <span className="max-w-[150px] md:max-w-[200px] truncate">{att.name}</span>
-                    <span className="text-xs text-muted-foreground whitespace-nowrap">
-                      ({formatFileSize(att.size)})
-                    </span>
+                    {canPreview ? (
+                      <button
+                        type="button"
+                        onClick={() => setPreviewAttachment(att)}
+                        title={att.name}
+                        className="flex items-center gap-2 min-w-0 hover:underline"
+                      >
+                        {label}
+                      </button>
+                    ) : (
+                      <div className="flex items-center gap-2 min-w-0">{label}</div>
+                    )}
                     <button
                       onClick={() => removeAttachment(index)}
                       className="ml-1 hover:text-red-500 min-w-[20px] min-h-[20px] flex items-center justify-center"
@@ -2242,7 +2304,8 @@ export function EmailComposer({
                     </button>
                   </div>
                 </div>
-              ))}
+                );
+              })}
               {attachments.length > 3 && (
                 <button
                   onClick={() => setShowAllAttachments(prev => !prev)}
@@ -2572,6 +2635,15 @@ export function EmailComposer({
           </div>
         </div>
       )}
+
+      {previewAttachment && (
+        <FilePreviewModal
+          name={previewAttachment.name}
+          onClose={() => setPreviewAttachment(null)}
+          onDownload={handlePreviewAttachmentDownload}
+          getFileContent={getPreviewAttachmentContent}
+        />
+      )}
     </div>
       <PluginSlot
         name="composer-sidebar-right"
diff --git a/components/email/email-viewer.tsx b/components/email/email-viewer.tsx
index 08b6d603..97c4b816 100644
--- a/components/email/email-viewer.tsx
+++ b/components/email/email-viewer.tsx
@@ -2899,7 +2899,10 @@ export function EmailViewer({
 <html style="color-scheme: ${colorScheme};"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1">
 <meta http-equiv="Content-Security-Policy" content="${iframeCsp}">
 <style>
-  html, body { overflow: hidden; }
+  /* Force content height: some emails set html/body { height: 100% }, which -
+     combined with overflow:hidden and our scrollHeight-based auto-resize -
+     collapses the measured height and clips everything below the fold. */
+  html, body { overflow: hidden; height: auto !important; }
   body { margin: 0; padding: ${bodyPadding}; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; font-size: 14px; line-height: 1.6; color: #1a1a1a; background: #ffffff; word-wrap: break-word; overflow-wrap: break-word; }
   @media (max-width: 640px) { body { padding-left: ${mobileBodyPaddingX}; padding-right: ${mobileBodyPaddingX}; } }
   img { max-width: 100% !important; height: auto !important; }
diff --git a/components/files/eml-preview.tsx b/components/files/eml-preview.tsx
new file mode 100644
index 00000000..aff7eb8e
--- /dev/null
+++ b/components/files/eml-preview.tsx
@@ -0,0 +1,110 @@
+"use client";
+
+import { useTranslations } from "next-intl";
+import { Paperclip, Download } from "lucide-react";
+import { sanitizeEmailHtmlForIframe } from "@/lib/email-sanitization";
+
+// A parsed message/rfc822 (.eml), as produced by postal-mime. Only the fields
+// this preview renders are typed.
+export type ParsedEml = {
+  subject?: string;
+  from?: { name?: string; address?: string };
+  to?: Array<{ name?: string; address?: string }>;
+  date?: string;
+  html?: string;
+  text?: string;
+  attachments?: Array<{ filename?: string; mimeType?: string; content?: ArrayBuffer | Uint8Array }>;
+};
+
+function formatAddress(a?: { name?: string; address?: string }): string {
+  if (!a) return "";
+  if (a.name && a.address) return `${a.name} <${a.address}>`;
+  return a.address || a.name || "";
+}
+
+function escapeHtml(s: string): string {
+  return s
+    .replace(/&/g, "&amp;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;")
+    .replace(/'/g, "&#39;");
+}
+
+// Renders a .eml attachment like an email: header (from/to/subject/date) + the
+// body, plus the message's own attachments. The body is sanitized with
+// DOMPurify AND rendered in a fully-locked sandbox iframe (sandbox="" - no
+// scripts, no same-origin), so a script-bearing .eml can never execute in our
+// origin. Parsing happens in the caller (FilePreviewModal); this is pure
+// presentation.
+export function EmlPreview({ message }: { message: ParsedEml }) {
+  const t = useTranslations("email_viewer");
+
+  const bodyDoc = message.html
+    ? sanitizeEmailHtmlForIframe(message.html)
+    : message.text
+      ? `<pre style="white-space:pre-wrap;word-break:break-word;font-family:ui-monospace,monospace;margin:0;padding:8px">${escapeHtml(message.text)}</pre>`
+      : "";
+
+  const downloadAttachment = (att: NonNullable<ParsedEml["attachments"]>[number]) => {
+    if (!att.content) return;
+    // content is a real ArrayBuffer/Uint8Array at runtime; cast for the strict
+    // BlobPart lib type (Uint8Array<ArrayBufferLike> vs ArrayBuffer).
+    const url = URL.createObjectURL(new Blob([att.content as BlobPart], { type: att.mimeType || "application/octet-stream" }));
+    const a = document.createElement("a");
+    a.href = url;
+    a.download = att.filename || "attachment";
+    document.body.appendChild(a);
+    a.click();
+    document.body.removeChild(a);
+    URL.revokeObjectURL(url);
+  };
+
+  return (
+    <div
+      className="w-full max-w-3xl max-h-full self-start overflow-auto rounded-lg border border-border bg-background shadow-2xl p-4"
+      onClick={(e) => e.stopPropagation()}
+    >
+      <h2 className="text-lg font-semibold text-foreground break-words">{message.subject || ""}</h2>
+      <div className="mt-2 space-y-0.5 text-sm text-muted-foreground border-b border-border pb-3">
+        {message.from && (
+          <div><span className="font-medium text-foreground">{t("from")}: </span>{formatAddress(message.from)}</div>
+        )}
+        {message.to && message.to.length > 0 && (
+          <div><span className="font-medium text-foreground">{t("to")}: </span>{message.to.map(formatAddress).join(", ")}</div>
+        )}
+        {message.date && (
+          <div><span className="font-medium text-foreground">{t("date")}: </span>{new Date(message.date).toLocaleString()}</div>
+        )}
+      </div>
+      {bodyDoc && (
+        <iframe
+          title={message.subject || "email"}
+          sandbox=""
+          srcDoc={bodyDoc}
+          className="w-full min-h-[55vh] mt-3 rounded bg-white"
+        />
+      )}
+      {message.attachments && message.attachments.length > 0 && (
+        <div className="mt-4 border-t border-border pt-3">
+          <div className="text-xs font-medium text-muted-foreground mb-2">{t("attachments")}</div>
+          <div className="flex flex-wrap gap-2">
+            {message.attachments.map((att, i) => (
+              <button
+                key={i}
+                type="button"
+                onClick={() => downloadAttachment(att)}
+                title={t("download")}
+                className="flex items-center gap-2 px-3 py-1.5 rounded-md text-sm bg-muted text-foreground hover:bg-muted/70"
+              >
+                <Paperclip className="w-3 h-3 flex-shrink-0" />
+                <span className="max-w-[200px] truncate">{att.filename || "attachment"}</span>
+                <Download className="w-3 h-3 flex-shrink-0 text-muted-foreground" />
+              </button>
+            ))}
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/components/files/file-preview-modal.tsx b/components/files/file-preview-modal.tsx
index ec9fd515..8422186b 100644
--- a/components/files/file-preview-modal.tsx
+++ b/components/files/file-preview-modal.tsx
@@ -6,6 +6,7 @@ import { X, Download, Loader2, ExternalLink } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { getFilePreviewKind, isMimeTypeSafeForInlinePreview } from "@/lib/file-preview";
 import dynamic from "next/dynamic";
+import { EmlPreview, type ParsedEml } from "@/components/files/eml-preview";
 
 // pdf.js-based inline viewer for mobile (no native inline PDF viewer). Loaded
 // only on the mobile PDF path so pdfjs-dist + its worker never reach the
@@ -153,6 +154,7 @@ export function FilePreviewModal({ name, onClose, onDownload, getFileContent }:
   // navigation. Blob URLs inherit our origin, so opening a script-bearing type
   // (text/html, image/svg+xml, ...) in a new tab would execute it in-origin.
   const [canOpenInNewTab, setCanOpenInNewTab] = useState(false);
+  const [emlContent, setEmlContent] = useState<ParsedEml | null>(null);
 
   // Decide whether to render the PDF in a plain <iframe> (desktop) or with the
   // pdf.js canvas viewer (mobile). navigator.pdfViewerEnabled is the standard
@@ -205,6 +207,7 @@ export function FilePreviewModal({ name, onClose, onDownload, getFileContent }:
     setContent(null);
     setObjectUrl(null);
     setCanOpenInNewTab(false);
+    setEmlContent(null);
     setLoading(true);
     setError(false);
     setResolvedFileType(getFilePreviewKind(name));
@@ -221,6 +224,12 @@ export function FilePreviewModal({ name, onClose, onDownload, getFileContent }:
         if (previewType === "text" || previewType === "markdown") {
           const text = await blob.text();
           if (!cancelled) setContent(text);
+        } else if (previewType === "eml") {
+          // Parse the embedded message (postal-mime, dynamic-imported so it
+          // stays off the bundle) and render it like an email via EmlPreview.
+          const { default: PostalMime } = await import("postal-mime");
+          const parsed = await new PostalMime().parse(await blob.arrayBuffer());
+          if (!cancelled) setEmlContent(parsed as ParsedEml);
         } else {
           // Stalwart's download endpoint can return generic
           // application/octet-stream for attachments even when the email's
@@ -329,6 +338,10 @@ export function FilePreviewModal({ name, onClose, onDownload, getFileContent }:
           </div>
         )}
 
+        {!loading && !error && fileType === "eml" && emlContent && (
+          <EmlPreview message={emlContent} />
+        )}
+
         {!loading && !error && fileType === "image" && objectUrl && (
           <img
             src={objectUrl}
diff --git a/lib/file-preview.ts b/lib/file-preview.ts
index 048bba23..77d24296 100644
--- a/lib/file-preview.ts
+++ b/lib/file-preview.ts
@@ -1,4 +1,4 @@
-export type FilePreviewKind = 'image' | 'html' | 'text' | 'markdown' | 'pdf' | 'audio' | 'video' | 'unsupported';
+export type FilePreviewKind = 'image' | 'html' | 'eml' | 'text' | 'markdown' | 'pdf' | 'audio' | 'video' | 'unsupported';
 
 const IMAGE_EXTENSIONS = new Set(['jpg', 'jpeg', 'png', 'gif', 'webp', 'svg', 'avif', 'bmp', 'ico']);
 const AUDIO_EXTENSIONS = new Set(['mp3', 'wav', 'ogg', 'm4a', 'flac', 'aac', 'opus']);
@@ -38,6 +38,12 @@ export function getFilePreviewKind(name?: string, type?: string): FilePreviewKin
     return 'html';
   }
 
+  // Embedded email message (e.g. a bounce/DSN, or forward-as-attachment).
+  // Rendered by parsing it and showing it like an email, not as a blob.
+  if (mimeType === 'message/rfc822' || ext === 'eml') {
+    return 'eml';
+  }
+
   if (mimeType === 'application/pdf' || ext === 'pdf') {
     return 'pdf';
   }