diff --git a/Ribbon.cs b/Ribbon.cs
index ba9d82e..85aa12a 100644
--- a/Ribbon.cs
+++ b/Ribbon.cs
@@ -43,8 +43,12 @@ public string Ribbon_LoadLabel(Office.IRibbonControl Control)
         #region IRibbonExtensibility のメンバー
 
         public string GetCustomUI(string ribbonID)
-        {
-            return GetResourceText("FlexConfirmMail.Ribbon.xml");
+        {
+            if (ribbonID == "Microsoft.Outlook.Explorer")
+            {
+                return GetResourceText("FlexConfirmMail.Ribbon.xml");
+            }
+            return "";
         }
 
         #endregion