Most likely has something to do with things like @ in email address. For example, this works:

use Mail::Sendmail;
my $me = "me\@aicompro.com"; 
  my %mail = ( To      => $me,
            From    => $me,
            Message => "This is a very short message",
smtp => 'mail.aicompro.com'


           );
  sendmail(%mail) or die $Mail::Sendmail::error;
[download]

This does not:

use Mail::Sendmail;
my $me = "me@aicompro.com";
  my %mail = ( To      => $me,
            From    => $me,
            Message => "This is a very short message",
smtp => 'mail.aicompro.com'


           );
  sendmail(%mail) or die $Mail::Sendmail::error;
[download]