I've never had the email/MMS gateways work. Personally I prefer JMP.chat which gives you a nice XMPP/MMS gateway and is much easier to work with.
In the US it wasn't an issue. What was the trouble? Keep in mind I was sending it to one or two people. I have no doubt it doesn't work on a mass scale.
I've only really tried AT&Ts gateways in the US from gmail, maybe something has changed but it never worked for me.
Edit: Super important. You can turn that feature off per phone number. You (or your recipients) may have told att not to send them