Contact Group Text

On my Z10 - OS release 10.2.1.3014. I have created a large Contract Group and I want to send a text mesages. I can select the group when I compose a text message, it converts it to a MMS, and then upon the sending of the text message I receive 'too many recipients'. Can someone tell me how many is too many.

I read somewhere that it was 10, but others have been able to send to more.
Don't know for sure though.