Whenever we track an inbound email, D365 tries to associate each participant of that email with entity records within dynamics (we’ve opted to not create new records automatically). When doing so for the „From“ field, this works as expected by selecting a single entity record based on an order documented in the linked article – usually this will be a systemuser or a contact record. But when it comes to the fields „To“ and „CC“, the system ignores this order and instead associates ALL records it was able to find for a given e-mail address. This search is VERY comprehensive and even included a custom e-mail field we created on the account entity, which made matters even worse. That custom field contained the address of our support hotline (support@domain.de) while the account records primary email address was set to a distribution list that included everyone located at our headquarters (cologne@domain.de) – and when someone chose Reply All to simply respond to an email, that email was used for the account.

The design documentation can be found here: https://docs.microsoft.com/en-gb/dynamics365/customer-engagement/admin/email-message-filtering-correlation#how-dynamics-365-for-customer-engagement-apps-associates-email-addresses-with-records

This should work in a more sensible way by treating all of these fields the same, and by using the documented "order priority". It's not useful to have the contact, system user, account, queue and whatever else has that same email address to be added to the To or CC field as activityparties, and as demonstrated with the Custom field on account, this can be seriously dangerous, too.

At the least give us the option to configure this in SOME way.