-->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)
))
))