Failed Attribute Change error with email field on new account creation

Let’s say user created an account, Customer.io received “create account” event and now there is a Customer.io person with following identifiers: cio_id - cio_id_1, id - id_1, email - test@email.com.

Let’s say we have “delete account” function. This function completely removes user’s account from DB, making its email available for complete new sign up. When user performs account deletion, Customer.io not receives “delete account” event because “delete account” function not sends it. 

Let’s say user with email test@email.com performed account deletion. Later this person decided to sign up from scratch. This person decided to use test@email.com again because it was released since last account deletion. So Customer.io receives “create account” event with following identifiers: id - id_2, email - test@email.com. Note that id is different because it is new account, but email is same. Customer.io creates person with following identifiers: cio_id - cio_id_2, id - id_2, email -. Email is missing.

In activity logs I see this error: activity type - Failed Attribute Change, activity name - email (identifier), value - test@email.com, reason - The identifier is already associated with a different profile.

Indeed, Customer.io have two persons. Old one with cio_id_1, id - id_1, email - test@email.com, and new one with cio_id - cio_id_2, id - id_2, email -. Because old person already have test@email.com, new person can’t use test@email.com. But from DB perspective it is completely two separate accounts. 

So my question is: how to assign email identifier to a new person if this email identifier already assigned to an old person?

I can’t call Customer.io API directly and trigger account deletion of old person because I’m calling Customer.io through Segment. In fact account deletion happens on backend side which is not aware of any analytics, including Segment and Customer.io. It frontend who triggers appropriate analytics events (through Segment) and account deletion API call. So with my current architecture it is not possible to tell Customer.io that user removed his/her account.