This applies to anyone running Cyanogenmod 10.1 (CM10.1) definitely, and most likely other ROMs such as AOKP, CM9, CM10 etc.
When one flashes a custom ROM, APN settings that are necessary to send/receive MMS are changed, because the default values are for Sprint.
DO THIS AT YOUR OWN RISK. While this worked fine for me, and you're not messing with anything too important, I am not responsible for anything you may do to your device.
Credit to Andrew Willing in the Ting forums for new method.
From the launcher/desktop, Add > Shortcut > Activities > com.android.sprintmenu > MMSC .MMSC
Use that shortcut to access your MMS URL. Change it to the correct URL for Ting, http://mms.plspictures.com
A note: stock AOSP messenger does not as of right now have code built in to send MMS over wifi, unlike Touchwiz or other. It might be worth looking into the Gnex or Nexus 4 to see if there's anything there.
- Root (assuming you're on a custom ROM, this is included)
- A root explorer such as ES File Explorer with root explorer enabled in settings
- A text editor capable of editing xml such as Jota+
- Open Voice Dialer, say "Open APN's"
- Check every one for an MMSC of "http://mms.sprintpcs.com"
- Change all instances of this to "http://mms.plspictures.com" and save
- Select one of the profiles with the correct MMSC in it.
- Open your root explorer, navigate to /system/etc and find apns-conf.xml
- Copy it to somewhere on your sdcard
- Open it and replace all instances of "http://mms.sprintpcs.com" with "http://mms.plspictures.com" and save.
- Copy and paste it back into /system/etc, ignoring warnings about overwriting
Please let me know if anyone has any problems or if this worked for you.
A note: It might be worthwhile to keep the edited copy of apns-conf.xml you made somewhere on your sd card, as whenever you update your ROM these settings go away. Simply copy and paste the edited file into /system/etc and recheck the other apns you get to from the voice dialer.