Hello,
1. Yes, the issue occurs with newly created accounts.
2. I haven't tried deleting the email address from the 'General' tab of a user's AD user properties. If there are some steps you'd like me to try, please provide them.
Also, the ADSI settings for proxyAddress is <none> for all users. For the one user that I tried to add the aliases to, I had two entries in the proxyAddress window:
STMP:email@domain.com
smtp:alias@domain.com
Thanks,
Zach