here is what i have for mms on sprint:
MMS Port: 80
everything else is: <not set>
these setting can be added to the default APN. no extra apn is necessary.
this will get the outgoing to work. incoming still is not working afaik.
pointless at this time as the sdcard is not working so we can not send out an mms with anything attached and no incoming. waiting for the sdcard to start working to continue working on this.
Model: Samsung Galaxy S3
ROM: changing all the time right now