Not to mention the providers will not tell you the limits to avoid spammers flying just below them, but you might find out once all your T-Mobile customers start to fail (silently of course). You get that one random number on an MVNO which for some reason unknown to the SMS provider just can’t receive SMS from your numbers.

I had forgotten the production go-live for critical functions for our client got pushed back like 6 months due to short codes getting approved at seemingly random schedules until you mentioned the approval process. I do not miss working with SMS.