Hi!
As far as your Xperia 10, there is a regression in jolla-messages and jolla-messages-settings that breaks MMS functionality in 4.3.0.12, at least on the 64-bit devices I’ve tried. It’s resolved by reverting to the previous versions of those apps. If you like, I can provide the RPMs. Further information located here, with a solution further down in the thread.
For your XA2, I looked around on the internet and tried to find the correct settings. Here’s what I found:
APN: internet
MMS Message center: http://10.81.0.7:8002
Proxy: 82.113.100.6
Proxy Port: 8080
I have no idea if these settings are correct, but I suppose you can try them. One thing to note, I had a similar issue with T-Mobile (in the US), where even though the settings were apparently correct, MMS wouldn’t work on my XA2. Setting the MMS APN to ipv6 worked. Of course, this may not work for you.
Can you provide me the settings you’re currently testing? I’ll do more research.
I hope this helps to some degree.