Just read Nate's blog post vodafone voice mail to email free which explains how to set up redirecting to get voicemail in email.

In Nate's example, does the call redirect occur at the phone level or at the telco network level? I see it is set on the phone, but just want to be sure of the effect.

My iPhone 3G has a simple call forward on/off option which I assume is all or nothing.

By the way, do the standard GSM redirect codes (http://en.wikipedia.org/wiki/Call_forwarding) work on the Vodafone network?

I am often out of coverage and getting voicemail in email messages would help a lot. Getting notification only of voice mail in email messages would be almost as good.