You seem to have picked a bad time to post -- looks like most monks are off to enjoy Christmas. Knowing nothing about Net::SMTP, I'd wildly guess that your problem has something to do with needing to specify binary mode. Looking (briefly) at Net::SMTP::Multipart, I wonder if that would be more applicable to your problem?

Hopefully someone actually knowledgable will wipe the eggnog from their chin and give you a real answer.

Merry Christmas!