I hope this answers the questions appropriately.
- Exchange account on separate server - the new account is also an exchange account
- I guess I mean email alias. e.g: exchange acount is ******@xxx.edu alias is: ******@xxx.edu
- Most people use the ******@xxx.edu - I also receive forwarded emails from the old account which was ******@separate.xxx.edu
- I'm not certain, but I believe it happens whenever I perform a "reply all." It certainly happens if the email was addressed to me with cc: to other individuals
- If I understand the question properly my response is: I only "reply all" when there were multiple addressees or people receiving cc: Some of them use the old exchange server, some the new one.