1. Click on Start button and type “Regedit” in Run option.

2. Here locate to :HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\UnreadMail

3. In right side panel, double click on the key MessageExpiryDays and set its value to 0.

4. If MessageExpiryDays key doesn’t exist, then in right side panel, click right to create a key with the nameMessageExpiryDays and then set its value to 0.

Now close the registry editor and restart your computer after any changes to go into effect.