test(preview): guard padding against characters spam filters count as hidden text

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: dielduarte

.changeset/quiet-marks-hide.md

@@ -2,4 +2,4 @@
 'react-email': patch
 ---
 
-Leave the direction marks U+200E and U+200F out of the `<Preview>` padding, so spam filters such as rspamd no longer score it as hidden text.
+Leave the direction marks U+200E and U+200F out of the `<Preview>` padding, so spam filters such as rspamd no longer score it as hidden text. The padding sequence is now `\xa0‌​‍`; if you post-process rendered HTML by matching the old sequence, update it.

packages/react-email/src/components/preview/preview.spec.tsx

@@ -18,6 +18,15 @@ describe('<Preview> component', () => {
     );
   });
 
+  it('pads only with characters spam filters ignore as preview padding', async () => {
+    const actualOutput = await render(<Preview>Short text</Preview>);
+    const padding = actualOutput.match(/<div>([^<]*)<\/div>/)?.[1];
+
+    // rspamd's HIDDEN_TEXT rule counts any other hidden character, so padding
+    // made of anything else gets scored as hidden text
+    expect(padding).toMatch(/^[\s\p{Z}​-‍]+$/u);
+  });
+
   it('renders correctly with really long text', async () => {
     const longText = 'really long'.repeat(100);
     const actualOutputLong = await render(<Preview>{longText}</Preview>);