Navigate to Contacts > Contacts/Smart Lists.
Click More Filters
Choose “Tag” and then select “Is” and choose the tag you will be using for failed SMS.
NOTE: You can use an existing tag or create a new one, such as “Failed SMS.”
Click “Apply” to save your filter.
At the bottom of the window, click “Save as smart list” to save the filter(s) as a permanent list. (You can always edit or delete this list later.)
Step 2: Create a Workflow to Apply Your Tag
Create a new Workflow in the workflow builder, and set up a trigger for “Twilio Validation Error”.
Filter by “Error Is” and choose “SMS Incapable.”
Save the trigger.
Add an action to the Workflow.
Choose “Add Contact Tag” and type in the name of the tag you created in Step 1 (such as “Failed SMS.”)
Save the action.
Save and publish your Workflow.
Now, anytime the Twilio system recognizes that an SMS fails/errors, the workflow automation will apply your “Failed SMS” tag to the contact. Your saved Smart List of Contacts will be updated in real-time with anyone who has that tag. You can then determine if you want to manually go through that list to resolve issues or create another workflow to automate another type of follow-up (perhaps a call or email) to those Contacts.
