[Dovecot] Are host names a secret?

Some time ago I added the ability for IMAP clients to fetch messages' GUIDs using FETCH X-GUID command. Because of a bug it wasn't working in 1.2.0 or 1.2.1, but I've fixed it now. But now I'm starting to wonder: With Maildirs the GUIDs are the maildir base filenames, which contain host names. Is it a bad idea to expose them to users?