When "validity" attribute prevents delivery of SMS

I had a query from a customer recently where they sent a SMS message to a handset residing on another Australian carrier. They received a 201 response and a messageID, however the message never got delivered to the handset. What went wrong? When you send an SMS you’ll notice there is an attribute called validity. In this case it was set to “validity” : “1”, which means the message will attempt to deliver for 1 minute before being discarded. When delivering messages across carriers (e.g. Telstra to Optus) it can at times take longer than 1 minute to deliver. Our suggestion is; when using validity for general use-case, set it to “60” or remove the attribute from the body where the network will then attempt to send the message for up to 7-days.