Should any disk folders on the VPOP3 server be shared?

VPOP3 supplies email to client computers using protocols such as IMAP4, POP3, etc, so you do not need to share folders on the VPOP3 server at all.

In general it is best NOT to share the folders, because that way users cannot cause damage to the VPOP3 configuration, and viruses on users computers cannot affect VPOP3's files.