How can I set up a Postfix mail server so that select users cannot delete emails from the server?

Question

postfix

I am a teapot.
There is a Postfix+Cyrus IMAP server on CentOS. Now half of the users are on Pop3, the other half on IMAP (there is not enough space on the server). It is necessary to set up permanent storage of mail of some users (without the possibility of deletion) + once a month, backup these letters to the storage system, just in case. as I understand it, after I googled, I need to dig towards imap + acl. The question is how to force selective users to connect only via IMAP and how to configure their ACL so that they cannot delete the letter from the server.
I am ready to express my gratitude in an unfiltered equivalent.

Answer 1

I solved this issue by disabling writing to the .Trash directory of a specific user using the Linux file system itself.

Answer 2

Postfix has nothing to do with it.
Cyrus, as far as I know, is not able to restrict access to itself according to protocols as you need it.
Alternatively, you can restrict firewall access to the POP port from certain IP addresses.