Do you think that ISP block third-party MMS servers?

[veso266]

Hi there, I tried to play around with your project, but when I entered my own MMSC in the url nothing came to the server

there is also MMS Proxy entry in my android settings, not sure if I have to fill that one too

Then when I tried to debug I have setup my own http server and set MMSC to it, but nothing came to it, and I know my server is acsessible over mobile data

for some reason I was able to proxy all my traffic via a web proxy (if I proxy section of APN settings) too see what's going on, but for some reason my Web Proxy (Fiddler) wasn't able to see any MMS traffic passing by when I sent an MMS
we are talking about android APN settings which look like this

but to no evil, I wasn't able to send MMS via my proxy, so is there a possibility that my mobile provider (Telekom Slovenije) blocks third-party MMS servers to force all the MMSes through their own servers?

Thanks for Anwsering and Best Regards