Error Message: "Error 351" or "Invalid Destination Address"

There are a vast number of error codes that carriers send back to TextPower to indicate why messages didn't get delivered.  One of the most frustrating is an "Error 351" or "Invalid Destination Address Value."  What does this mean and how can you resolve it?

What this typically indicates is that the carrier has blocked short code messages from being delivered to this particular phone number. They may also be blocking users from sending messages to short codes. If this is the case the users will have to contact the carrier to ask them to "remove the short code block."

Note that even though the message is failing the carrier charges TextPower for these attempts to send a message through their system, therefore you are charged by TextPower.  In an effort to eliminate these unproductive charges, anytime a number generates a 351 error it will be automatically opted out of the keyword.  This prevents repeated charges.  Once the issue is resolved (see below) the mobile user will have to text your keyword to the system in order to opt back in.  

Why does this occur? There are a few potential reasons, in order of most likely to least likely:

  1. It is possible that the number you are sending to is not a mobile number but rather is a “VoIP” line (voice over IP), the most popular type of “landline” now being purchased by homeowners that do want a landline.  These numbers can potentially receive text message even though they are not assigned to mobile devices.  The national cellular database does not reject the numbers so it is possible the number is opted because during the initial lookup process to determine whether the number is a mobile or landline it will be recognized as a mobile number.  When trying to send to that number, however, we will receive the “Error 351” message from the upstream aggregator that the number is not assigned to an actual mobile device. 
  2. If the customer has recently ported their mobile number from one carrier to another (e.g., AT&T to Verizon Wireless) the carrier may not process text messages to or from short codes - this does not affect "peer-to-peer" messaging which is when one mobile number sends to another mobile number - until after the billing has been established or the final details of the port are completed.  
  3. The phone may be on a prepaid plan and does not have sufficient credit to receive additional messages.
  4. T-Mobile does not deliver text messages to their resellers' numbers.  There are exceptions to this and it does not always apply in cases of T-Mobile errors but it is a strong possibility if the number in question is on either T-Mobile's direct service or through one of their resellers. 
  5. The number may have been deactivated for non-payment at one time and even subsequent to the past due amount being resolved.
  6. At one time the number was on a plan that restricted the reception of messages from short codes. 

There are other miscellaneous reasons why a "short code block" may have been imposed but it can be a mystery even after talking to carriers.  

How do we resolve this error?

It may be resolved by having the mobile user text "HELP" to the short code to which they are assigned to and see if they get TextPower's standard response. If they do receive it then have them text your keyword as an attempt to opt-in.  If that works then the issue has been fixed.  If not then you will have to ask them to contact their carrier and ask them to “remove the short code block.“  This almost invariably works if the first approach does not.  Sometimes TextPower can work behind the scenes on behalf of the mobile user to remove the short code block but it is far more effective and faster for the customer to simply call their carrier.  

These procedures resolve 99% of these errors.  If after taking all of these steps the problem still exists please contact TextPower directly.

Note that a related error, shown as “4720 - Not a cell phone” is different.  This error indicates that the number to which a message was attempted is a landline number and is not capable of receiving text messages.  Numbers that experience this error will also be automatically opted out of the keyword.  No process can opt these numbers back in because they are not text-enabled in any case.