Improved error message

app/src/main/java/eu/faircode/email/FragmentMessages.java

@@ -5396,7 +5396,7 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                     if (is == null) {
                         if (message.identity != null)
                             db.identity().setIdentitySignKeyAlias(message.identity, null);
-                        throw new IllegalArgumentException(context.getString(R.string.title_invalid_key));
+                        throw new IllegalArgumentException(context.getString(R.string.title_unknown_key));
                     }
                 }
 

app/src/main/res/values/strings.xml

@@ -817,6 +817,7 @@
     <string name="title_certificate_invalid">Public key of %1$s is invalid</string>
     <string name="title_no_key">No private key</string>
     <string name="title_invalid_key">Invalid private key</string>
+    <string name="title_unknown_key">Private key does not match encryption key</string>
     <string name="title_send_plain_text">Plain text only</string>
     <string name="title_send_receipt">Request receipt</string>
     <string name="title_send_receipt_remark">Most providers and email clients ignore receipt requests</string>