I dont know why you think avast uses alot of ram as on all my systems it only uses about 4 to 6 meg and around 9 meg when browsing with several tabs open, but anyway if you dont have an installed mail client you can uninstall the mail shield via remove programs, double click avast as to remove then click change and when you get the popup screen simply untick the options you dont want then ok, you might have to reboot after running.