MimeBodyPart intermediatary = new MimeBodyPart();
intermediatary.addHeader("Content-Transfer-Encoding", "base64");
intermediatary.setDataHandler(new DataHandler(new ByteArrayDataSource(new FileInputStream(serviceHeaderPath), "Application/pkcs7-mime smime-type=enveloped-data;")));
String strdisposition = "attachment; filename = "+strp7File;
intermediatary.setDisposition(strdisposition);

/////////////////////
This generates the following header:

Content-Type: Application/pkcs7-mime; name=Rnifp7c.p7c
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename = Rnifp7c.p7c

But I need to set Content-Transfer-Encoding : base64 [as i am passing the base64 encoded content]

SO HOW DO I SET THIS Content-Transfer-Encoding to Base64 ??