How to setsubject in base64 encoding in mimemessage

Question

Hi,

While i send mail using javamail API i set the subject likr this

msg.setSubject(subject,charset);

But this setsubject method encode subject only in Quoted-printable encoding. But i want to setsubject in base64 encoding.

For Example:

Expected result: =?big5?B?............?=

result obtained: =?big5?Q?.............?=

please help me. Thanks in advance