How to get and copy mail by condition (for example, by sender)?

Question

Mail server

Colleagues, good afternoon!
I just can’t find a solution to such a problem, or rather a tool for solving it:
There is mail for a domain, relatively speaking on Yandex. Letters come to the employee in his Thunderbird, where his mailbox is configured, for example [email protected] There are some boxes, for example [email protected], which receive letters that can be addressed to others, including the above [email protected] This box is connected to an employee who, roughly speaking, sorts out these incoming letters and:
1) looks from whom it is from, the contents of the letter, possibly an attachment, that is, any information that can help identify the person to whom it needs to be redirected;
2) if the addressee is found - the letter goes to this employee from his client, if not - goes to the department that processes these applications in the usual manner;
There was a task to automate it. I understand that no bot can fully replace a person, however, I would like to implement a simple algorithm:
1) some software interacts with several inboxes (that is, with an external Yandex mail server);
2) if the incoming letter in the "FROM" field contains information that is in the database of the client-employee link. You can dynamically get this data from the CRM system, where there is this bundle of clients and their mail, and transfer it to processing for mail sorting - it copies the letter to the employee's mailbox, which is actually taken from this database. That is, relatively speaking - we determine that this is a client already working with the company;
3) if the incoming letter is not identified, it goes to the letter processing department, that is, we say that this is a new client.
Apparently, it is also possible to study the contents of the body of the letter, if you parse it with some tool, and then also make a decision based on this.
Amendment (12/23/20):Perhaps I did not quite correctly describe the essence of the problem. It is necessary on some intermediary server, between [email protected] with mailboxes on it and programs on the employees' PCs, to implement the processing of letters. That is, accept, look under what conditions it fits (described above in the algorithm), then, according to these conditions, redirect the letter to one employee or to another employee. Letters come to a certain general mailbox, but they can be and are addressed to a specific person, so you need to redirect such letters to people. Initially, look at the sender's address, then you can complicate it (would be possible).
Question: how is such a scheme implemented? That is, how to receive mail, how to redirect, and so on. Postfix or something else, or a bundle? (I didn’t have a chance to work with mail servers, there was simply no need).

Answer 1

Since you already have Thunderbird installed, then implement the necessary actions with its own forces:

Настройки (Меню Thunderbird) -> Инструменты -> Фильтры сообщений

An important condition for sorting messages between different mailboxes is that Thunderbird works with mailboxes using the IMAP or IMAPS protocol.
You make as many rules as you need and there is no connection to any mail service such as Yandex, mail.ru, ukr.net or your own mail server.
On the screenshot, an example of one rule:

PS The only disadvantage of this implementation is the constantly running Thunderbird for processing/copying/moving correspondence between mailboxes or folders. If the computer never turns off and Thunderbird is always on, then there will be no issues with sorting letters.

Answer 2

And the built-in filters on Yandex - Rules for processing incoming mail?
There you can set conditions by the field from whom, and by subject, and by the content of the letter