NSMutableArray *userList = [userDefaults objectForKey:@"userList"];
    if(userList){
        if(![userList containsObject:self.email]){
            [userList addObject:self.email];
        }
    }else{
        userList = [NSMutableArray array];
        [userList addObject:self.email];
    }
    [userDefaults setObject:userList forKey:@"userList"];
    [userDefaults synchronize];