diff --git a/src/lib/__tests__/emailHtml.test.ts b/src/lib/__tests__/emailHtml.test.ts
index 1ef7d24..0f9b9b6 100644
--- a/src/lib/__tests__/emailHtml.test.ts
+++ b/src/lib/__tests__/emailHtml.test.ts
@@ -42,6 +42,13 @@ describe("prepareHtml", () => {
     assert.ok(result.includes("img[width]{display:block!important"), "inline images should stack instead of forcing a giant row");
   });
 
+  it("emulates common responsive email helper classes in readable mobile mode", () => {
+    const result = prepareHtml("<html><head></head><body><table class='flexible'></table><td class='hide'></td><span class='db'>x</span></body></html>");
+    assert.ok(result.includes('table[class~="flexible"]{width:100%!important'), "flexible tables should expand to the available width");
+    assert.ok(result.includes('[class~="hide"]{display:none!important'), "gmail spacer rows should be hidden in mobile readable mode");
+    assert.ok(result.includes('[class~="db"]{display:block!important'), "db helper classes should become block elements");
+  });
+
   it("listens for parent width messages from EmailBody", () => {
     const result = prepareHtml("<html><head></head><body>hi</body></html>");
     assert.ok(result.includes("iframe-parent-width"), "should accept parent width postMessages");
diff --git a/src/lib/emailHtml.ts b/src/lib/emailHtml.ts
index b74bde7..b963411 100644
--- a/src/lib/emailHtml.ts
+++ b/src/lib/emailHtml.ts
@@ -103,6 +103,9 @@ export function prepareHtml(
     'html[data-mobile-friendly="true"] table,html[data-mobile-friendly="true"] table[width]{width:100%!important;max-width:100%!important;table-layout:auto!important}',
     'html[data-mobile-friendly="true"] td,html[data-mobile-friendly="true"] th,html[data-mobile-friendly="true"] td[width],html[data-mobile-friendly="true"] th[width]{width:auto!important;max-width:100%!important;min-width:0!important}',
     'html[data-mobile-friendly="true"] img,html[data-mobile-friendly="true"] img[width]{display:block!important;max-width:100%!important;width:auto!important;height:auto!important}',
+    'html[data-mobile-friendly="true"] table[class~="flexible"]{width:100%!important;max-width:100%!important}',
+    'html[data-mobile-friendly="true"] [class~="hide"]{display:none!important;width:0!important;height:0!important;max-width:0!important;max-height:0!important;min-width:0!important;overflow:hidden!important;padding:0!important;font-size:0!important;line-height:0!important}',
+    'html[data-mobile-friendly="true"] [class~="db"]{display:block!important}',
     'html[data-mobile-friendly="true"] pre,html[data-mobile-friendly="true"] code,html[data-mobile-friendly="true"] blockquote{overflow-wrap:anywhere;word-break:break-word}',
   ].join("");