rfc3391-6: When a message is split across multiple chunks, the chunks need
not be contiguous. 

rfc3391-8:Additional chunks contain messages or partial messages that
represent some component of the compound object. 

rfc3391-10:A message can be broken into multiple parts and each break
can occur anywhere within the message.  

rfc3391-11: Each part of the message is zero or more bytes in length
and each part of the message is the contents of its own chunk.

rfc3391-12: The order of the chunks within the
Application/Vnd.pwg-multiplexed entity must be the same as the order
of the parts within the message. 

rfc3391-13:the message may contain a Content-Type header to specify
 the content-type of the message content.  Also, the message may
 contain a Content- ID header and/or Content-Location header to
 identify a message that is referenced from within another message.
 If a message contains no Content-Type header, then the message has an
 implicit content-type of "text/plain; charset=us-ascii"

rfc3391-14: each message in an Application/Vnd.pwg-multiplexed entity
has a unique message number, and a message consists of the
concatenation of all the octets from the one or more chunks with the
same message number.

rfc3391-15: The isMore field of the chunk header of the last chunk of
each message must have a value of "LAST" and the isMore field of the
chunk header of all other chunks must have a value of "MORE".