diff --git a/dom/html/nsTextEditorState.cpp b/dom/html/nsTextEditorState.cpp
index 2e1f1f986b2..9b19b9b6d45 100644
--- a/dom/html/nsTextEditorState.cpp
+++ b/dom/html/nsTextEditorState.cpp
@@ -1298,6 +1298,13 @@ nsTextEditorState::PrepareEditor(const nsAString *aValue)
     }
 
     newEditor = mEditor; // just pretend that we have a new editor!
+
+    // Don't lose application flags in the process.
+    uint32_t originalFlags = 0;
+    newEditor->GetFlags(&originalFlags);
+    if (originalFlags & nsIPlaintextEditor::eEditorMailMask) {
+      editorFlags |= nsIPlaintextEditor::eEditorMailMask;
+    }
   }
 
   // Get the current value of the textfield from the content.