- Clear the cache for the Messenger app. To do this, go to Settings > Apps. Swipe left until you bring up the All Apps column. Scroll down and find the Messaging app. Tap the Clear Cache button. Do NOT press the Clear Data button as this will destroy your messaging history.
- Add a “1” to the beginning of the number you are sending the MMS to. Instead of (###)###-####, change the number in contacts to 1(###)###-####
- Contact your service provider to verify you are using the correct APN setting and your SIM card is working properly.
- Check with your service provider to ensure that their network allows unlocked phones to send MMS.
