421 4.2.0 sender rejected AUP#SNDR

Thank you so much for this info.  It is extremely frustrating.  I completely agree with having a "spam" folder for the texts they are blocking.  We utilize a 3rd party app at work.  Which has 2 factor authentication set up.  This means the cell companies know the texts are coming from a legitimate site.   We would text are technicians info in the field directly from our software.  These guys are electricians who don't have computers readily available when they are at a customers home.  Not having this feature is really causing issues.  What it comes down to is all the carriers want people to pay for sending texts like these.  It doesn't matter that we as a company pay our cell phone bill and the recipient of these texts pay their own bill...they want to bill us on top of that.  Absolutely ridiculous.  Why when I am driving down the road and I pass a Kohls, I will receive a text about some coupon they are currently offering but if I sent a text from an authenticated app it doesn't go through????