My personal rules of eMail:  

1)  I don't  put anyone in Bcc: without notifying all recipients, as in,  putting "Bcc:ing unrevealed recipients" under signature

2)  I DO put people unknown to each other
in Bcc: stating clearly "unrevealed recipients" or
"selected individuals" in To: so they know NOT to use
"reply to all" if they want to remain private 

3)  I do not share my eMail Contacts without permission

4)  I nearly always put myself in Cc: so
the recipient knows who is writing to them, and
I have a copy in my Folders for reference 

5)  I try to verify whether information is permissible to
share

6)  I DO look for messages and try to answer people
in a timely way

7)  I DO save everything in Folders that I can "search"
easily with my Gmail which is wonderful, easy and free