$mail_reg  = qr{\W*(\.*(?:\w+|-)+(?:\.\w+|-)*\@\.*(?:\w+|-)+(?:\.\w+)+)\W*};
$mail_1    = '<smtp:"email.address@something.something.something.com">';
$mail_2    = '<smtp:emailaddress@something.something.something.com>';

$mail_1 =~ m#$mail_reg# and print $1, $/;
$mail_2 =~ m#$mail_reg# and print $1, $/;

# which outputs:
# email.address@something.something.something.com
# emailaddress@something.something.something.com