The Huawei HG659 VDSL modem/router that is supplied by Vodafone with VDSL connections does not have NAT Loopback capability. This feature is only required if you run a webserver and/or email server that is connected to the same local area network as your VDSL connection AND you want to access your email or website(s) with a computer that is connected to the same local area network.
Access to these services from outside your local area network is not a problem.
The only workaround is to replace the Huawei unit with a VDSL modem/router that does have NAT Loopback. One choice would be the D-Link DSL-2870B Dual Band Wireless Modem/Router that supports both ADSL and VDSL. It can be readily purchased here in NZ for around $249. I purchased mine from Harvey Norman.
It would be nice if Vodafone could get Huawei to supply a firmware update that includes the NAT Loopback feature.