Note: The following might be considered off-topic. On the otherhand, there might be something nefarious in the SMS network. I found something strange that affects SMS in Canada. You can send the lower case text "secure communication", but it will never be recieved by the recipient. I am not sure if this behavior is reproducible outside of Canada. It might be a software defect, or perhaps there is something capturing…
I can't verify it is send over SMS or MMS though. In theory there's no reason for my cellphone to send it over MMS.
The exact word used: secure communication