Why is there only one person in my contacts that I can't send a MMS text message? However I can receive their MMS texts

Hello laurenblairf,

Thank you for using Apple Support Communities.

For more information, take a look at:

iOS: Troubleshooting Messages

http://support.apple.com/kb/ts2755

To resolve issues with sending and receiving MMS, follow these steps

1. Go to Settings and turn airplane mode off.
2. Go to Settings > Messages and turn MMS Messaging on.
3. Go to Settings > Cellular and turn Cellular Data on.
4. Go to Settings > Cellular and turn Data Roaming on if you're roaming on a cellular provider network that is different from your billing provider's network.
5. Make sure that you have a cellular data connection in the status bar of your iPhone.
6. Go to Settings and turn Wi-Fi off. Open Safari and navigate to www.apple.com to verify that you have a data connection. Turn Wi-Fi back on to continue using Wi-Fi for other features. If your cellular data connection isn't available, follow these steps.
7. Make sure that you can send and receive SMS. If you can't send and receive SMS, see the "Issues with sending and receiving SMS" section, above. MMS might not be available while you're on a call. Only 3G and faster GSM networks support simultaneous data and voice calls. Learn more about which network your phone supports.
8. Restart your iPhone.
9. Tap Settings > General > Reset > Reset Network Settings on your iPhone.
10. Remove your SIM card and insert it again.

Have a nice day,

Mario