Autofill only populates if you have sent them email from webmail (not from the client)
To delete an autofile from webmail you have to use the up and down arrow keys and the Delete key rather than being able to click on an X
We have many shared accounts and multiple users that need access to those accounts. They currently have to login to the other account by selecting the dropdown and change accounts.
They cannot access shared folders or shared address books because of this either
You can create rules in OWA but the steps and windows are different than the client which confuses people.