Release Quarantine Mail to different Recipient Address

I have a question about release of emails from user "per-recipient quarantine" accounts.

The fortimail is connected by ldap to the Active Directory.

Example:

We have an OnPrem Exchange with a mailbox abc@domain.com.

To this account a secondary mail address xyz@domain.com is assigned.

The mail was sent to xyz@domain.com and the user want to release the mail, but the release mail never arrived at the mailbox abc@domain.com. So I created an alias (abc@domain.com -> xyz@domain.com) but this doesn't resolve my issue.

After g...ling the issue I detected this page:

https://cookbook.fortinet.com/fortimail-troubleshooting-antispam-issues/

The sender’s email address in the release message was not the same as the intended recipient of the email that was quarantined. If you have configured your mail client to handle multiple email accounts, verify that the release/delete message is being sent by the email address corresponding to that per-recipient quarantine. For example, if an email for user@example.com is quarantined, to release that email, you must send a release message from user@example.com.

But how?

I checked the user preferences at the fortimail for this account and there is a setting for identities. Could this be the solution? Only add a second identity (xyz@domain.com)?

It would be nice if anybody have any suggestions or have the same behavior and it's own solution for that.

Thanks a lot...