use strict;
use warnings;
use Win32::OLE;
use Win32::OLE::Const 'Microsoft Outlook';
use Mail::Outlook;

  my $outlook = new Mail::Outlook();
  my $folder = $outlook->folder('Drafts');
  my $message = $outlook->create();

  my %hash = (
     To      => 'user@mail.com',
     Subject => 'Blah Blah Blah',
     Body    => 'Yadda Yadda Yadda',
  );

    $message->save();

##</code><code>##

  my $doc = Win32::OLE->GetObject($message);
  my $property = 'X-ICCategory';
  my $value = '2';
  

  my $docprops =  $doc->CustomDocumentProperties();
  unless (defined ($doc->CustomDocumentProperties($property)))
  {
    $docprops->Invoke('Add', {
                               Name => $property,
                               LinkToContent => 0,
                               Type => 4,
                               Value  => $value,
                              });
   }
  $doc->CustomDocumentProperties($property)->{Value} = $value;