Do not delete addresses from the copy of the email

[il2020]

1. customer1 starts the conversation and adds customer2@example.com to the copy of the email.
2. customer2 replies to everyone in the email and adds customer3@example.com to the copy.
3. customer3 sends an automatic reply saying that he is currently on vacation, only to the Freescout email address. No one is copied.

Now, when a user replies in the conversation, only customer3@example.com is listed in the copy.

It would be better if customers could never remove emails from the copy, but could only add them. That is, if an address ever appeared in the copy, only the user could remove it.

PHP version: 8.2.29
FreeScout version: 1.8.197
Database: MySQL
Are you using CloudFlare: No
Are you using non-official modules: Yes

[il2020]

There is another case when the necessary address is not included in the copy of the email.

1. customer1 starts a conversation with the addresses customer2@example.com and customer3@example.com in the copy.
2. The user replies in the conversation and adds another address to those two: customer4@example.com.
3. customer4 replies to the email and only includes those two addresses in the copy. They do not include themselves in the copy.

When the user replies again, only customer2@example.com and customer3@example.com are included in the copy. customer4@example.com does not see the reply.