i use Aspose.Email.dll (19.3.0.0) for test msg to mht in vs2010.
But when some Japanese mails are converted into MHT format, the mailing title and attachment name become random code. Unlike the original mail, it can not be read normally.
I have worked over your requirements and have been able to observe the issue. An issue with ID EMAILNET-39458 has been created in our issue tracking system to further investigate and resolve the issue. This thread has been linked with the issue so that you may be notified once the issue will be fixed.