fault MIME charset to be used for
 mail messages is different than the charset used for files stored on
 the system, this property should be set. <p>

 The current implementation also supports the following System property.
 <p>
 The <code>mail.mime.ignoreunknownencoding</code> property controls
 whether unknown values in the <code>Content-Transfer-Encoding</code>
 header, as passed to the <code>decode</code> method, cause an exception.
 If set to <code>"true"</code>, unknown values are ignored and 8bit
 en