Apparently this problem is a symptom of Mail running in multitask mode. Here is a simple fix that should work for you until the problem is addressed by Apple.
Quit the Mail app from the multitask bar.
Here’s how to do it:
- Click the Home button to exit the Mail app.
- Double-click the Home button to bring up the multitask bar listing currently “open” apps.
- Locate the Mail app icon in the multitask bar.
- Tap and hold the icon until the red minus sign appears.
- Tap the red minus.
- The Mail icon will vanish. You have now completely quit the Mail app.
- Double-click the Home button to exit the multitask bar.
When you next launch Mail the messages with no sender and no content should be gone.
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