Multiple "To:" and "Cc:" header lines in SMTP messages

["O'Brien, Walt" <Walt_OBrien@xxxxxxxxxxxxxxxxxxx>]

I have recently come upon occurances of SMTP mail gateways producing
messages with more than one "To:" or "Cc:" field.

Can anyone point me to references to discussions of this behavior?

This behavior is explicitly allowed in RFC 822.  On page 16 in section
4.1 it states:

		This specification permits multiple  occurrences  of  most
 		fields.   Except  as  noted,  their  interpretation is not
		specified here, and their use is discouraged.              

There are no further notes relative to multiple occurances of "To" or
"Cc" header lines that I can
find.

Thanks,
	Walt