diff --git a/app/src/main/java/eu/faircode/email/HtmlHelper.java b/app/src/main/java/eu/faircode/email/HtmlHelper.java
index 7d25d3a3e6..e1721660c5 100644
--- a/app/src/main/java/eu/faircode/email/HtmlHelper.java
+++ b/app/src/main/java/eu/faircode/email/HtmlHelper.java
@@ -4215,6 +4215,14 @@ public class HtmlHelper {
                     .attr("name", "viewport")
                     .attr("content", "width=device-width, initial-scale=1.0");
 
+        // https://stackoverflow.design/email/base/mso/
+        if (!doc.body().select("mark").isEmpty())
+            doc.head().append("<!--[if mso]>\n" +
+                    "  <style>\n" +
+                    "    mark { background:yellow; mso-highlight:yellow; }\n" +
+                    "  </style>\n" +
+                    "<![endif]-->\n");
+
         for (Element span : doc.select("span")) {
             if (span.attr("dir").equals("rtl")) {
                 Element next = span.nextElementSibling();