The use of personal e-mail addresses is a known security risk. Considering your administrators have access to employee PII Data (Personally Identifiable Information), it is highly likely that your IT Team already have a policy of not allowing the use of personal e-mail addresses for sensitive logins.
To help you prevent them being used, we block certain domain names. If you try and use a restricted domain for an administrator account, you will see the following error message:
"Sorry, you cannot use this email address (Learn More)."
This doesn't affect your employee accounts, they can use any e-mail address.
Can you turn off this restriction?
Yes, please contact support if you understand the risks and want to allow personal e-mail addresses to be used. We highly recommend that you enable Two Factor Authentication on your account, if you haven't already done so.