-->Go to List -->list settings -->Click Email Column-->Go Column Validation Type below Formula
--> and Write Error message "Enter Correct Email"
=AND(ISERROR(FIND(" ",Email,1)),IF(ISERROR(FIND("@",Email,2)), FALSE,AND(ISERROR(FIND("@",Email,FIND("@",Email,2)+1)), IF(ISERROR(FIND(".",Email,FIND("@",Email,2)+2)), FALSE,FIND(".",Email,FIND("@",Email,2)+2) < LEN (Email) )) ))