The Archive service allows for role-based rights, by which specific users may be delegated access to the archived messages of one or more users at the same domain.
Access to all archived messages associated with an email address, can be delegated to one or more users, via the Management > Archive > Access Rights section of the control panel. The privileged users must have the archive service enabled for their own mailboxes, and must be part of the same domain as the archive(s) they are given access to.
The service does not permit chained delegation. For example, if Alice has access to Bob's archive, and Bob has access to Charlie's archive, Alice will NOT automatically receive delegated access to Charlie's archive.