'D' and 'C' are valid as topic tags on the subject line, because they are the
shortest unique forms of valid topic names (dog, cat).

I interpreted the original message to mean that the questioner wanted to know if
it was possible to prevent the topic name from appearing on the subject line of
the message. If I interpreted the question correctly, the answer is 'No'. If
there is no valid topic tag at the beginning of the subject line, the message is
automatically assigned the topic 'Other'. The subject line is not changed, but
the message is distributed only to those subscribers who have selected 'Other'
or 'All' as their topic options.

--
Paul Russell
Senior Systems Administrator
University of Notre Dame