My parents use Sprint, I use Verizon. We both have Samsung Galaxy smartphones. I have the Verizon Galaxy S6 and they have the Sprint Galaxy S4. I started using the Verizon Message + app for texting and whenever I send them a MMS it comes in as a blank text message from me, but if they long hold on the message, they have an option to "Save Attachment", once they save it, they can then look in their download folder and see the picture I sent. Why is it that when using the Message + app for sending MMS it shows up on their end as a blank message. I have adjusted their phones to make sure it will load MMS and retrieve MMS, but it still didn't do anything. They can send me MMS and I receive them just fine, but when I send them MMS it doesn't work.
On a side note, I switched back to the default texting app that came with my Samsung Galaxy S6 and I was able to send MMS to my parents with out an issue. Any thoughts as to why the Verizon Message + app has difficulty sending MMS to Sprint customers using an older model of Samsung Galaxy smartphone?