Unluckily, your suggestion doesn't seems to work. I managed to substitute chars, but parts() method starts complaining for the raw string, as you already guessed in your comments. That's why I tried to modify as following: 

..
print Dumper \$ent;

my $aref=[];
my $oldr=$ent->{mail_inet_head}->{mail_hdr_list};
foreach (@$oldr){
  my $n=$_;
  $n=~s/\n/\r\n/g;
  push(@$aref,$n);
}

$ent->{mail_inet_head}->{mail_hdr_list}=$aref;
#       exit;

my $result = SOAP::Lite
          ->packager(SOAP::Packager::MIME->new)
          ->parts([$ent])
          ->proxy($create_proxy, ssl_opts => [ SSL_verify_mode => 1, S
+SL_ca_file => '/root/Firefox_CERT/CUSTOMERROOTCA2'] )
          ->call($header, $method => @data)
;

[download]

This actually override \n in header section, but the request is still not accepted by remote server throwing a 500 error. I'm still confused because MIME::Entity is only building a little block of the final HTTP request (the encoded binary file with his headers), I guess SOAP::Packager is adding lot of things like multipart etc. I'll try to deepen with curl changing only 1 row at a time to see which section of the request is causing the behaviour. In the meanwhile, suggestions are welcome

In reply to Re^2: Again on SOAP::Lite, MIME::Entity and SOAP::Packager by ray.rick.mini
in thread Again on SOAP::Lite, MIME::Entity and SOAP::Packager by ray.rick.mini

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