As the poster above noted, uninstalling an application on your phone does not stop an external site from still trying to contact your phone. Think of it this way. Would deleting someone's name from your addressbook stop them from calling you? You have to turn off the contact at the source. The same thing would happen if you sign up for Mobile Email alerts on one phone and started using another phone without the Mobile Email application installed. You woulld have to use the old phone or another phone with Mobile Email to sign back into the Mobile Email program to turn off the alerts. It becomes really frustrating if you inherit a phone number from someone who did not turn off the alerts. You cannot sign on to Mobile Email to turn off the alerts because you do not have the email account information of the other user.
OZMail runs most of the email and instant message features of Mobile Email on AT&T phones with that application.