B-D (or Bacula-Digest) is an attempt to make Bacula the network backup solution a bit better. B-D will act as an interface between Bacula job control and the message sending part of Bacula. The reason for doing this is that Bacula tend to be a bit chatty from time to time.
The basic idea is that an administrator do not need to know when the job was perfectly fine executed, Bacula offers the solution to not send mail at all. That would prevent even the messages an administrator do want, when the job did not execute correct. The aim in B-D is to take all messages and check if they indicate that all was OK or not.
These details are provided for information only. No information here is legal advice and should not be used as such.