Alias Not Working

Hi,

I am trying to add an alias under Accounts…>General> email >Aliases …>Add Alias

When I do so and then Save out of there and then go back to the New Mail window, I get the original name and nothing more. When I check the alias is still visible in its place but not in the dropdown next to the send button.

If I restart the client the alias is gone when I restart!

Can anyone suggest a solution?