While helping one of  our users sending a piece of mail to  an - in terms
of networks - far  away user I got a rejection  which first seemed weird.
It consisted  of four or five  headers added by UAs  containing path- and
routing information  and other nonsense  comments. The last one  was from
a daemon  which said  *unbalanced "*  - but there  was no  indication how
the  "To:"-field looked  when it  received it.  Of course  the "To:"  and
"From:" changed their contents at every UA on the way ...
The address  was long but otherwise  simple and contained a  true name in
the form "Joe J. Jones" we tried it  with "Joe J Jones" - see, it worked.
And the form  of the rejection Mail  - I don't think  LISTSERV would have
been able to  make any sense out  of it ... it was almost uninterpretable
for the human postmaster :-) ....
Christian