I compare with other mail server. I find the MIME like this:
Content-Type: image/gif;
name="=?gb2312?B?yP3Wu7LKx/IuZ2lm?="
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="=?gb2312?B?yP3Wu7LKx/IuZ2lm?="
but Zimbra mail server sent mail MIME like this:
Content-Type: image/pjpeg
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="& .jpg"
that the zimbra mail server not appoint the attachment filename use which coding , I guess If you
appoint the filename use the ISO8859-1 , like this:
filename="=?ISO8859-1?yP3Wu7LKx/IuZ2lm?=". I think it's will be not problem with the chinese attachment filename.