Enigmatic share /dovecot

As soon as I install the “active directory domain controler” package from the app center, a share “dovecot” is created that I can access from windows PCs (\\myservername\dovecot). The listed contents correspond to /usr/lib/dovecot on the UCS-Server.
This share is listed nowhwere with “testparm -s” or other samba commands.
Is there any explanation? More “hidden” shares like this (might be a security issue)?

Steps to reproduce:

same applies to \\myservername\backup → /var/backups