This is not recommended or supported for email programs. While it may seem to be a good solution to synchronize your messages and folders among different computers, .pst (Outlook) files in particular were intended to be stored and accessed from a local hard drive only.

Reading and writing from your email program on a computer to email data files on a network drive increases the time it takes and are more likely to become corrupted. For more details see Microsoft's support article on Limits to using personal folders (.pst) over LAN and WAN links.