And some B2B+B2C SaaS products (Box/Dropbox/etc), when encountering this situation, only let 1 account exist. When the IT department tries to provision a conflict, instead of being provisioned, the personal account goes into an "invited to assimilate" status. The end user gets an email asking them to allow their account, which was created personally, to be converted to one managed by the enterprise admin. The user gets an opportunity, before the IT admin has control, to migrate personal data out (if they want the account converted) or change the email address to something that wouldn't conflict (if they want 2 accounts).