You can check off the checkmarks beside the emails. A bar should show up at the bottom of the screen and you can select Delete. Alternately, you can choose select all from the menu, and again hit delete.
gmail or email?(I'm assuming email)If you want to delete the message permanently;Goto the settings menu while in the email app (bottom left button, the three lines)Choose account settingsScroll down to "Incoming Settings"Scroll down to "Delete email ...
Check the Manufacturers website for the phone. Try to download / install the latest firmware for Rogers.Backing up your data on the phone may or may not work depending on the custom ROM that was installed.