Understanding and reviewing your SMS deliverability

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You will learn

Learn the important aspects of SMS deliverability, including how to evaluate it and best practices.

For SMS, deliverability is defined as whether or not a text message successfully made it to a recipient’s mobile device. Regularly reviewing SMS performance is key to maximizing your ROI, maintaining high customer engagement rates, and avoiding carrier filtering.

The importance of SMS consent

Before we jump into deliverability, it’s important to understand SMS consent. Most countries require you to get explicit consent from subscribers. This means that:

  • You must make it clear that providing a phone number means agreeing to receive SMS marketing messages
  • Other forms of consent (like opting into email) do not count as consent for SMS

In Klaviyo, someone must be opted in to receive a text message from your brand. If there’s no SMS consent on the customer profile, the phone number will be skipped automatically.

How a text message is delivered

There are three contributors involved in whether or not your recipients receive a text message:

  1. Your SMS marketing platform (e.g., Klaviyo)
  2. The wireless carrier (e.g., AT&T, T-Mobile, Verizon, etc.)
  3. The individual’s phone or mobile device
SMS marketing platform

The SMS marketing platform is where you create and send your messages. The platform may perform certain checks before a message goes out to recipients. Klaviyo, for instance, will prevent you from sending to anyone who hasn’t consented to SMS. Klaviyo will also check the content of the message to see if it contains any non-compliant terms, specifically those related to sex, hate, alcohol, firearms, or tobacco (SHAFT) as well as illegal activity or substances, like CBD or hemp.

Wireless carriers

If the message passes the SMS marketing platform’s checks, it moves on to the wireless carriers. The carriers will perform their own checks, again looking for SHAFT/illegal terms in the message, URL, or linked landing page as well as what type of sender you are (e.g., your sending number type, engagement rate, unsubscribe rate, etc.) Each carrier has its own criteria for these checks and will filter SMS and MMS messages as they see fit. Carriers will sometimes provide a reason for a failed delivery, but this is not always the case. They sometimes don’t confirm delivery or failure at all to prevent people from learning more about their checks and how to get around them.

Individual's mobile device

The final component to deliverability is the recipient’s device. Once the wireless carrier approves, the message should arrive to the individual’s phone. However, it could still not be delivered if, say, the phone is off or in a location without service. Android devices can also filter messages into a spam folder, rather than showing them in the main SMS inbox.

How to evaluate SMS deliverability in Klaviyo

There are a few key metrics to consider when evaluating your SMS performance. These include:

  • Click Rate
    The percentage of recipients who clicked the link within the SMS message
  • Conversion Rate
    The percentage of recipients who clicked the link within the SMS message and made a purchase within your SMS conversion window
  • Number of Subscribers
    The number of people subscribing to receive your SMS communications
  • Unsubscribe Rate
    The number of customers unsubscribing from your SMS communications
  • Resubscribers
    The number of customers who opted out from your communication and opted back in

Review your campaigns

The table below breaks down what’s considered good for SMS and MMS campaigns

  Click rate Conversion rate Unsubscribe rate
SMS campaigns 10.5–14.5% 1.0–2.0% 0.6–1.0%
MMS campaigns 10.7–14.7% 2.0–3.0% 0.2–0.8%

Monitor these ranges based on the last three campaigns you have sent. If the averages are worse (lower for the click and conversion rates, but higher for the unsubscribe rate) than what’s listed here, you should take action. 

First, make sure you’re using segments to target the right audience for messages. Also, examine the content and timing of your message, asking yourself the following questions:

  • Have I made it clear to recipients who this message came from?
  • Am I sending to the right audience?
  • Am I sending too often/not often enough?
  • Does the message contain a URL? Is it working correctly?
  • Do recipients know what to expect from the URL?
  • How easy is it for recipients to unsubscribe?

We also recommend sending from either a verified toll-free number or short code. Note that toll-free numbers take around 7–10 days to be verified. 

Review your flows

The table below breaks down what’s considered good for SMS and MMS flow messages.

  Click rate Conversion rate Unsubscribe rate
SMS flows 11.3–15.3% 2.7–3.5% 1.4–1.8%
MMS flows 10.9–14.9% 3.9–4.7% 1.8–2.2%

With SMS flows, review performance on a per-message basis. As with your campaigns, examine the content of the message, including the link, opt-out text, call to action, etc.

Further, look at the surrounding splits and time delays to make sure that the right group got your message when they were meant to. Also, consider whether or not to use Smart Sending by asking yourself how important it is for subscribers to see the message.

Evaluate your failed deliveries

Pay attention to your failed deliveries. Ideally, the failed delivery rate should be as low as possible. If you’re seeing a lot of failed deliveries, review the failure reasons:

  • Device Disconnected means that the device is no longer in service, which can mean:
    • The destination number is unknown or no longer exists.
    • The device you are trying to reach does not have sufficient signal.
    • There is an issue with the mobile carrier.
  • Device Unreachable means that the device is not in a service area, not accepting messages, or the device is off. It’s similar to a soft bounce for email.
  • Carrier Violation means that the phone carrier filtered the message out.
  • Message Blocked means that a wireless carrier, Klaviyo's system, or the recipient has blocked the message.
  • Device Incapable of Receiving SMS means that the number is a landline or cannot receive SMS. Klaviyo will automatically unsubscribe the phone number if this is the failure reason.
  • Unknown means that the wireless carrier did not report why a message was not delivered.

For Device Disconnected or Device Incapable of Receiving SMS, you may want to turn on double opt-in for your SMS list, if it isn’t on already, to prevent non-working numbers from joining your lists.

If you’re seeing Carrier Violation or Message Blocked, review your message, link, and landing page so that there are no references to SHAFT, CBD, etc. Check that you are following all best practices for your SMS messages.

The same is true if the failure reason is Unknown, since the carrier hasn’t provided more information. Further, you may want to either get a short code or use a verified toll-free number. Keep in mind that you must apply for verification/short codes and not every business or industry is eligible.

Best practices for SMS deliverability

There are several ways to improve or maintain your SMS deliverability:

  • Use segments to better target your subscribers (e.g., grouping by engagement, purchase history, and interests).
  • Use a trusted sending number, such as a short code or verified toll-free number.
  • Turn on double opt-in for your SMS lists.
  • Never use SHAFT-related words or references to CBD, hemp, and other prohibited content.
  • Send only between 9 a.m. and 8 p.m. in the recipient’s local time (for flows, we recommend keeping SMS quiet hours enabled).
  • Make sure recipients know who the message is coming from, such as by mentioning your organization's name in your message or using a branded sender ID.
  • Include opt-out language or a link (required in most countries).
  • Send around 2–6 SMS messages per month.

Additional resources

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