Shared folders using mbox format

Hi,

I'd like to create a shared folder to be used with an Outlook client and a Thunderbird client. We're currently using mboxes.

I've read the documentation here about creating a shared folder: https://wiki.dovecot.org/SharedMailboxes/Shared

It doesn't make reference to how to do this using mbox format. Is it possible? Should we convert to Maildir? Perhaps there's a way to provide both formats?