Email name restrictions?

Email name restrictions?

I'm trying to move to Zoho Mail and getting existing user accounts set up, but I’m seeing a "! AS101" alert when trying to add certain email addresses (or aliases). They are: facebook@<mydomain> instagram@<mydomain> personal_ebay_recovery@<mydomain> They're addresses used for our existing corporate Facebook, Instagram and an Ebay login, so it's fairly important to add these addresses in order to use Zoho email. Is there a 'block' on using certain words in an email address? If so can it be removed or overridden?