I'm using a SAMSUNG SGH-i917 at the moment (because my Galaxy Nexus died), and am trying to get MMS & 3G working.
I've managed to get 3G going by entering the following into the APN settings:
Settings > Cellular > edit apn
User name: <blank>
Proxy server/URL: 188.8.131.52
Proxy port: 8080
I've tried sending an MMS, and almost instantaneously get a notification that the message cannot be sent.
Has anybody got any experience in getting MMS working on the Samsung SGH-i917?