c:\@Work\Perl\monks>perl -wMstrict -le
"my $sentto = 'Fred Flintstone (US) (fredf@gmail.com)';
 ;;
 my $captured =
 my ($first, $second) =
 $sentto =~ m{ \A (.*) \s+ ([(] [^(]* [)]) \z }xms;
 ;;
 if ($captured) {
   print qq{first '$first'   second '$second'};
   }
 else {
   warn 'parse failed';
   }
"
first 'Fred Flintstone (US)'   second '(fredf@gmail.com)'
[download]

(I don't like using  $& and friends.) (Update: Also, the regex assumes the second parenthetic group has no nested parentheses!)