I have a user Sales which I show in Outlook as a supplementary box for all users in sales departament. I'd like them to view the messages in the account Sales, but without possibility to delete any messages. I'd like to designate one of the sales users to be able to delete the messages from the box periodically, or even configure the automatic archiving on it. I've already tried this command: Add-MailboxPermission -Identity "Sales" -User jdoe -AccessRights ReadPermission -InheritanceType All but then users have no access at all to the account. The only setting that works seems to be FullAccess Is there a way to prevent users from deleting messages from a box to which they have permissions?

FullMailbox means they can delete a message and you cant prevent it. Why not just give them reviewer rights to the inbox only? You can do that via Outlook.

There's a lot of users in the departament, so I was hoping to find a solution at the server level. Is there really no other way to set user rights (or maybe mailbox permissions)?

I would create a mail-enabled security group and apply the reviewer permissions to that group. You can also use pfdavadmin to apply delegate permissions at the central level.