New CentralAccount value being incorrectly calculated QER_BuildCentralAccount (4382578)

The BuildCentralAccount script is seemingly only impacting a new joiner with a specific name.

No person exists with a first name and a last name in the Person table as confirmed in the Object Browser with the SQL query: SELECT CentralAccount, DefaultEmailAddress, LastName, FirstName FROM Person WHERE LastName = '<LastName>' AND FirstName = '<FirstName>'

Relevant tables for target systems were also queried and no account was found.

The enabled QER | Person | CentralAccountGlobalUnique configuration parameter considers O365/Exchange Online Mail Contact email addresses (which must be external) in its collision via the function CallFunction("SearchCentralAccount", accntPrefix + "%").  

In Designer | Edit configuration parameters | QER | Person | CentralAccountGlobalUnique configuration parameter is enabled.

• NOTE: If this configuration parameter is set, the central user account for an identity is formed uniquely in relation to the central user accounts of all identities and the user account names of all permitted target systems.
• Reference document: Identity's central user account

In Designer | One Identity Manager Schema | Tables | Person | CentralAccount | Value calculation tab.

The OOTB calculation of the central user account is made up of the first name and the first letter in the last name of the identity. This can be adjusted to the organization's requirements, for example:

• Dim centralaccount As String = QER_BuildCentralAccount(Entity, Function() String.Format("{0}.{1}", $Firstname$, $Lastname$)).

In here it is seen that it has been customized to a format of Firstname, a dot, and then the Lastname (e.g.: Joe.Doe@contoso.com). Which matches common organizational email address format. 

Steps to reproduce:

Verified that a new identity template value calc test for Miguel Cespedes would create Miguel.Cespedes, note that person object is not actually saved/created.

Then added a new mail contact, miguel.cespedes@(...) inside Exchange Admin Center and ran the Exchange Online sync. 

Re-testing the identity creation for centralaccount and its collisions. The central user account is now Miguel.Cespedes.2
It's confirmed that the collision is happening because of the existence of an Exchange Mail Contact.

Enabling QER\Person\CentralAccountGlobalUnique considers O365/Exchange Online Mail Contact email addresses (which must be external) in its collision via the function CallFunction("SearchCentralAccount", accntPrefix + "%"). 

The main point being:

1. The configuration parameter is defined as searching against "the user account names of all permitted target systems". The wording is not clear on this topic, in addition to Entra ID accounts and Exchange Mailboxes, Exchange Mail Contacts are considered under this definition.

The below options can be considered to resolve this issue:

1. In this situation, the offending mail contact could be removed to avoid the collision
2. An administrator can disable or set the configuration parameter in Desinger for QER\Person\CentralAccountGlobalUnique to 0