diff --git a/components/email/email-composer.tsx b/components/email/email-composer.tsx
index 309f8c57..44a67ca5 100644
--- a/components/email/email-composer.tsx
+++ b/components/email/email-composer.tsx
@@ -30,7 +30,7 @@ import { useContactStore, getContactDisplayName, getContactPrimaryEmail } from "
 import { useTemplateStore } from "@/stores/template-store";
 import { SubAddressHelper } from "@/components/identity/sub-address-helper";
 import { generateSubAddress } from "@/lib/sub-addressing";
-import { substitutePlaceholders } from "@/lib/template-utils";
+import { substitutePlaceholders, spliceTemplateAboveSignature } from "@/lib/template-utils";
 import { TemplatePicker } from "@/components/templates/template-picker";
 import { TemplateForm } from "@/components/templates/template-form";
 import type { EmailTemplate } from "@/lib/template-types";
@@ -1094,7 +1094,16 @@ export function EmailComposer({
 
     if (mode === 'compose') {
       setSubject(filledSubject);
-      setBody(bodyContent);
+      // Compose bodies carry the embedded signature (see
+      // shouldEmbedSignatureInNewMail) and the send path assumes it stays
+      // there, so replace only the message content, not the signature block.
+      if (plainTextMode) {
+        setBody(shouldEmbedSignatureInNewMail
+          ? appendPlainTextSignature(bodyContent, signatureIdentity, { separator: signatureSeparatorEnabled })
+          : bodyContent);
+      } else {
+        setBody((prev) => spliceTemplateAboveSignature(prev, bodyContent));
+      }
       if (template.defaultRecipients?.to?.length) {
         setTo(template.defaultRecipients.to.map(parseRecipient));
       }
@@ -1115,7 +1124,7 @@ export function EmailComposer({
     }
 
     setShowTemplatePicker(false);
-  }, [mode, plainTextMode]);
+  }, [mode, plainTextMode, shouldEmbedSignatureInNewMail, signatureIdentity, signatureSeparatorEnabled]);
 
   useEffect(() => {
     const handleTemplateKey = (e: KeyboardEvent) => {
diff --git a/lib/__tests__/template-utils.test.ts b/lib/__tests__/template-utils.test.ts
index 8ec0dd14..1a4fd8c4 100644
--- a/lib/__tests__/template-utils.test.ts
+++ b/lib/__tests__/template-utils.test.ts
@@ -10,6 +10,7 @@ import {
   filterTemplates,
   exportTemplates,
   importTemplates,
+  spliceTemplateAboveSignature,
 } from '../template-utils';
 import type { EmailTemplate } from '../template-types';
 
@@ -333,3 +334,39 @@ describe('filterTemplates', () => {
     expect(filterTemplates(templates, 'xyz')).toHaveLength(0);
   });
 });
+
+describe('spliceTemplateAboveSignature', () => {
+  const template = '<p>Template body</p>';
+
+  it('keeps the signature block below the template (separator marker)', () => {
+    const prev = '<p></p><p data-signature-block="separator">-- </p><div>My signature</div><p data-signature-block="end"></p>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="separator">-- </p><div>My signature</div><p data-signature-block="end"></p>'
+    );
+  });
+
+  it('keeps the signature block below the template (start marker, no separator)', () => {
+    const prev = '<p>old draft text</p><p data-signature-block="start"></p><div>My signature</div><p data-signature-block="end"></p>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="start"></p><div>My signature</div><p data-signature-block="end"></p>'
+    );
+  });
+
+  it('replaces the whole body when there is no signature block', () => {
+    expect(spliceTemplateAboveSignature('<p>old draft text</p>', template)).toBe(template);
+  });
+
+  it('keeps everything from the start marker onward when the end marker is missing', () => {
+    const prev = '<p>old</p><p data-signature-block="separator">-- </p><div>My signature</div>';
+    expect(spliceTemplateAboveSignature(prev, template)).toBe(
+      '<p>Template body</p><p data-signature-block="separator">-- </p><div>My signature</div>'
+    );
+  });
+
+  it('discards user edits above the signature', () => {
+    const prev = '<p>half-written draft</p><p data-signature-block="separator">-- </p><div>Sig</div><p data-signature-block="end"></p>';
+    const result = spliceTemplateAboveSignature(prev, template);
+    expect(result).not.toContain('half-written draft');
+    expect(result).toContain('Sig');
+  });
+});
diff --git a/lib/template-utils.ts b/lib/template-utils.ts
index a693ef89..ca12ffc6 100644
--- a/lib/template-utils.ts
+++ b/lib/template-utils.ts
@@ -80,6 +80,26 @@ export function filterTemplates(templates: EmailTemplate[], query: string): Emai
   );
 }
 
+// Compose bodies carry the embedded signature bracketed by
+// data-signature-block markers (see email-composer's
+// buildEmbeddedSignatureHtml). Applying a template must replace only the
+// message content, so splice the template above the signature range instead
+// of overwriting the whole body.
+export function spliceTemplateAboveSignature(prevHtml: string, templateHtml: string): string {
+  const doc = new DOMParser().parseFromString(prevHtml, 'text/html');
+  const startEl = doc.querySelector('[data-signature-block="separator"], [data-signature-block="start"]');
+  if (!startEl) return templateHtml;
+  const endEl = doc.querySelector('[data-signature-block="end"]');
+  const host = doc.createElement('div');
+  let cursor: Node | null = startEl;
+  while (cursor) {
+    host.appendChild(cursor.cloneNode(true));
+    if (cursor === endEl) break;
+    cursor = cursor.nextSibling;
+  }
+  return templateHtml + host.innerHTML;
+}
+
 function sanitizeText(value: unknown): string {
   return DOMPurify.sanitize(String(value || ''), STRIP_HTML_CONFIG);
 }