Whose accounts you can invite into EA Portal as administrator role?

As you know, you can utilize Azure EA Portal to create new Azure subscriptions to charge from your EA contract. Microsoft will send an invitation mail to an account which your company has own. The account will be invited as Enterprise Administrator. Refer to an article below if you need to confirm each role on EA Portal.
normalian.hatenablog.com

Next, you need to invite accounts as new administrator roles. You have to confirm which account types are available to be invited, because there are two account types below.

• Microsoft Account
  • This account type is also called as "Personal Account"
  • Microsoft manages this account type
  • This account type isn't one of Microsoft Azure resources
  • You could create Microsoft Account by using your corporate mail address such like yyyy@normalian.xyz in past, but you can do that no longer
• Work or School Account
  • Azure Active Directory tenant has these accounts
  • Sync thesee accounts from on-premise Active Directory into Azure Active Directory tenant
  • This account type is one of Microsoft Azure resources

You need to utilize these accounts on EA Portal. You can find "Auth Level" menu on EA Portal below and choose a proper option to invite new administrators.

Difference of Auth Level on EA Portal

There are four types of "Auth Level" you can choose. Assume your organization has "normalian.xyz" Azure Active Direcotry tenant and here are diagrams which account types you can invite.

Other tips

#1 You will find error messages below if you choose wrong Auth Level. Change proper Auth Level option to invite your accounts.

#2 Wizard to add new administrators will be changed like below.

#3 There is no effect for your existing administrator accounts even if you will change "Auth Level" after inviting the accounts.

#4 It seems to take a little bit time to reflect change of Auth Level, because it sometimes failed to invite new accounts just after changing Auth Level.