diff --git a/app/src/main/java/eu/faircode/email/Helper.java b/app/src/main/java/eu/faircode/email/Helper.java
index 674e327cfd..2ad39a921f 100644
--- a/app/src/main/java/eu/faircode/email/Helper.java
+++ b/app/src/main/java/eu/faircode/email/Helper.java
@@ -517,7 +517,7 @@ public class Helper {
 
             // Check if viewer available
             if (ris == null || ris.size() == 0) {
-                if ("application/ms-tnef".equals(type))
+                if (isTnef(type))
                     viewFAQ(context, 155);
                 else {
                     String message = context.getString(R.string.title_no_viewer,
@@ -530,7 +530,7 @@ public class Helper {
             try {
                 context.startActivity(intent);
             } catch (ActivityNotFoundException ex) {
-                if ("application/ms-tnef".equals(type))
+                if (isTnef(type))
                     viewFAQ(context, 155);
                 else {
                     String message = context.getString(R.string.title_no_viewer,
@@ -541,6 +541,12 @@ public class Helper {
         }
     }
 
+    private static boolean isTnef(String type) {
+        // https://en.wikipedia.org/wiki/Transport_Neutral_Encapsulation_Format
+        return ("application/ms-tnef".equals(type) ||
+                "application/vnd.ms-tnef".equals(type));
+    }
+
     static void view(Context context, Intent intent) {
         Uri uri = intent.getData();
         if ("http".equals(uri.getScheme()) || "https".equals(uri.getScheme()))