I have been seeing and using the symbols + or ++ whenever a new recipient is added to an existing email thread along with the original recipients in To or Cc.
Just curious about how this came into practice. Is there a definitive understanding of how + or ++ is being used in today's email communications?
Raising this question here as am not sure if this is the right site in stackex.
UPDATE: To clarify, the + or ++ symbols are added in the body of the email, not in To or CC.