I know this is a SUPER old thread - but THANK YOU! I was wondering why my attached PDF was coming up with an error about the font not being accessible. I was doing:

      push @parts, Email::MIME->create(
          attributes => {
              filename     => $filename,
              content_type => "application/pdf",
              encoding     => "quoted-printable",
              name         => $filename,
          },
          body => io( $opts->{attach_file} )->binary->all,
      )
[download]

But tweaked it to use base64 and it works fine now:

      push @parts, Email::MIME->create(
          attributes => {
              filename     => $filename,
              content_type => "application/pdf",
              encoding     => "base64",
              name         => $filename,
          },
          body => io( $opts->{attach_file} )->binary->all,
      )
[download]

Would never have thought of that!