I just got a new Vodafone Japan phone to mess around with the network. In particular, I'm curious about how SMS evolves or fails to evolve in Japan.
So here's what I tested. I have a T-Mobile US SIM in a Nokia phone and was able to send and receive SMSs over both the Vodafone 3G network and the NTT DoCoMo 3G network. I was able to send an SMS to my Vodafone Japan phone, but not to my NTT DoCoMo phone. However, I was NOT able to reply to the SMS. As far as I can tell, but Vodafone Japan and DoCoMo disable sending SMSs to any other network than their own, but Vodfhone Japan allows you to receive an SMS from outside the network. This is for people with accounts on those networks. Their networks DO allow people who roam on their networks to send and receive SMS freely.
I am going to Finland tomorrow so I will try to use my Vodafone Japan phone there and see if it still blocks my SMS. I have a feeling that since the SMS server is probably where they block it, that it probably won't change anything.
The good news is that the 3G networks in Japan allow 3G phones and 3G subscribers from outside of Japan to roam on the Japanese networks. The bad news is that the Japanese networks are bringing their old-fashioned closed network philosophy and crippling connectivity between their networks. How stupid.