How to save copies of incoming / outgoing letters of users of the organization?

Question

Mail for domain

Good afternoon.
Please tell me, there is not a large organization of 20 users. It has its own mail, in the form of "Yandex mail for domain", which suits everyone. But the management had a desire to have copies of letters received / sent by employees.
There has already been a similar question. The CEO wants to read all incoming mail in the organization
But the solutions there are "heavy"
Maybe someone will tell you a simpler solution, how to make mailbox mirrors? It is desirable not passing a mail traffic through "himself"?

Answer 1

And how are you going to save copies of letters without running them through your piece of iron?
From "easy" solutions - copy-paste :D

Answer 2

Yandex supports collecting mail from other mailboxes. If there are not many employees, create a monitoring box and add collectors for employee boxes to it. If the number of employees exceeds the limit of collectors, you can organize a chain - collect into several intermediate boxes and from them collect into the final one.