May I know how I can disable the "Excluding" feature once and for all,
for the email notification?

I believe I have made too many changes in the email preference
settings for users and myself that I can no longer predict who can and
who cannot receive the emails regardless of whether they are assignee,
reporter and even not in default cc list.

The thing is everyone in the team is closely knitted and would like to
help out if any bug appears. Email load is no issue as company's
servers are powerful enough for the 3 months project. Sometimes, these
emails provide reminders (as we won't be checking for bugs all the
time) and it should be up to individual user to decide what mails to
keep or dispose.

So, really appreciate any help.
Thanks in advance.