my $mailcmd ="/usr/lib/sendmail -t -n -oi";
my $recipient = "recipient\@domain.com";
my $msg_text = "your message";

open  SENDMAIL, "| $mailcmd" or die $!;
print SENDMAIL "From: user\@domain.com\n";
print SENDMAIL "To: $recipient\n";
print SENDMAIL "Subject: testing 123\n\n";
print SENDMAIL $msg_text;
close SENDMAIL;