use Net::SMTP;

my $smtp = Net::SMTP->new(
    "localhost",
    Hello => 'localhost.localdomain',
    Timeout => 15,
    Debug => 1,
);
$smtp->mail( $sender );
if ( $smtp->recipient( $recipient ) ) {
    $smtp->data();
    my $msg = $entity->stringify;
    while ( $msg =~ m/([^\r\n]*)(\r\n|\n\r|\r|\n)?/g ) {
        my $line = ( defined($1) ? $1 : "" ) . "\r\n";
        $smtp->datasend( $line );
    }
    if ( $smtp->dataend() ) {
        print( STDERR, "Message sent!\n" );
    } else {
        print( STDERR, "Failure sending data.\n" );
    }
} else {
    print( STDERR, "Rejected recipient.\n" );
}
$smtp->quit();