[imp] BCC privacy problem?

[Joseph Brennan]

>> This seems to be a privacy problem with IMP, but I've been unable to
>> find a definitive source that says what the proper behaviour should be
>> in the absence of To and CC lines but I seem to remember that the MUA
>> (IMP) should add "To: undisclosed-recipients;" in the absence of any
>> other To or CC information.

RFC 822 requires one of the To or Cc header in a message.  It takes a 
careful reading of the syntax to see this.  My attention was drawn to
this when I learned the hard way about an MTA popular in Britain that
rejects mail lacking both To and Cc.  

The usual solution is to insert a null list into the To header,
which is "string:;" where string is conventionally "Undisclosed
recipients".  
 
RFC 2822 does not require To or Cc to exist, but older software is
still around, so better to insert a dummy To than not.

Joseph Brennan                           postmaster@columbia.edu
Academic Technologies Group, Academic Information Systems (AcIS)