Hi @Christine,

Welcome to the Community! I hope to work together with you so we can get to the bottom of what might be going on here regarding your SMS issue.

Like with email, deliverability of SMS is not guaranteed. After Klaviyo triggers a text message to be sent, Twilio passes that message along to the carrier networks who determine if the message can be delivered to the recipient. There are a number of reasons why a text message might not be delivered. For Device Disconnected errors, some possible causes are below:

• The destination number you are trying to reach is unknown and may no longer exist.
• The device you are trying to reach is not on or does not have sufficient signal.
• The device cannot receive SMS (for example, the phone number belongs to a landline)
• There is an issue with the mobile carrier

As a side note, for this particular error type, because the causes aren't always permanent, we don't automatically remove SMS consent. If you are ever cleaning your SMS lists, you might choose to segment for users who have had the device disconnected error multiple times and have 0 successful deliveries, and then remove consent for those users. However, we will auto-remove consent if the failure reason is definitely permanent (number invalid, carrier deactivated).

Sometimes, customers notice these issues occurring because they are using just one Long Number to send to a large amount of contacts. As outlined here, we generally recommend that you add an additional Long Number for every 200 profiles who opt into SMS marketing from your business. It is more common for carriers to filter messages coming from Long Numbers than it is for Short Codes. I'd recommend taking a look at this doc which goes over some best practices as well as how to add additional Long Numbers to your account: Improving SMS Deliverability when Using Long Numbers.

If you are uninterested in having multiple Long Numbers, I would recommend looking into using a Short Code. Here is our resource that covers the differences between the two and what you can expect with Short Code: How to Choose an SMS Sending Number.

I hope this helps clear this up!

Alex

Alex, you mentioned creating a segment for users who have had the device disconnected error multiple times and have 0 successful deliveries, and then removing consent for those users. 

Is there a help article on how to create this segment? Every SMS my company sends has about 300 failed sends and I’d like to clean up our SMS list and stop wasting credits on undeliverable messages.

Hey @Emily.C! We have a super handy step-by-step guide on this topic now :)

• How to clean SMS lists