Partial Org:
1. Our client needs all users and their multiple email addresses to be captured by Einstein Activity Capture. From what I understand, this isn't possible, correct?
https://help.salesforce.com/s/articleView?id=sf.aac_limitations.htm&type=5
2. Additionally, some users are already connected from Outlook to Salesforce via an email address that is simply used as a domain for Microsoft but not an active email address. How can these connections be deleted?
What it shows in this help article is not possible in the partial org we are working with:
Andrew Russo (BACA Systems) 
Forum Ambassador
1, correct its not goign to capture all.
2: go into full setup and you need to remove the org level EAC connection that an admin setup for EAC.
turn this off :https://help.salesforce.com/s/articleView?id=sf.aac_setup_org_level_connection.htm&language=en_US&type=5
