SMS Deliverability Strategic Guide & Best Practices - Klaviyo
2026-03-10 19:10 Diff
https://www.klaviyo.com/marketing-resources/sms-deliverability-guide

Understanding SMS deliverability and best practices

The marketer’s guide to SMS deliverability

SMS marketing is a powerful way to deliver value directly to your subscribers’ devices. But the success of your SMS campaigns and flows hinges on one crucial factor: deliverability.

To help you maximize the impact of your marketing efforts, we’ve put together this comprehensive guide on SMS deliverability best practices.

Understanding the ins and outs of SMS deliverability

What is SMS deliverability? This term is used in slightly different ways from business to business, so we’ll clarify the definition before jumping into best practices.

Put simply, SMS deliverability is the percentage of time that your messages are reaching their intended subscriber’s mobile device.

To calculate your deliverability, just divide the number of successfully delivered messages by the total number of recipients and multiply by 100.

But how do you actually move the needle on this metric? To answer this, it may be helpful to  first explore the factors that might impact your SMS performance.

3 critical factors that impact SMS deliverability

The type of phone number you use may affect your SMS deliverability. Some of the most common options include:

  • Toll-free numbers: Toll-free numbers are 10-digit numbers that begin with an 8XX prefix and are only available in the US and Canada. These numbers need to be verified, which may take around 7–10 days to process.
  • Dedicated short codes: Short codes are typically 5–6 digits. Brands must apply to get a short code, which takes time. But because of this process, short codes are more trusted by wireless carriers. Short codes are a good option for brands that want to avoid heavy filtering or want to send more than 30,000 messages at once.
  • Long codes:Long codes are country-specific. For example, if you have an Australian long code, you can’t send messages to anyone in Ireland. One of the benefits of long codes is that they allow you to receive inbound messages. Long codes have to be verified in Australia and Ireland, which may take 1–3 business days to complete.
  • Branded sender IDs: With branded sender IDs, you can set your brand’s name as the sender ID or number when you send one-way text messages. The same branded ID can be used across countries. There is a registration process for branded sender IDs in Australia, which takes 7–10 days to complete.

Steps to review your SMS deliverability performance

To improve your overall performance, we recommend focusing on 3 metrics:

SMS delivery rate refers to the percentage of subscribers who received your message, while SMS fail rate refers to the percentage who failed to receive your message.

The goal, of course, is to keep your delivery rate high and your fail rate low. To do this, it’s important to pay attention to how often your messages are failing to send.

While you can typically expect a small number of failed messages, you want to take action if the rate is too high. Specifically, if you’re receiving error messages for more than 5–10% of your total send, you may want to consider some of the following actions:

  • Enabling double opt-in: Double opt-in is a feature where the SMS subscriber receives a message asking them to confirm that they want to receive communications from your brand. For example, the message might say: “Reply YES to confirm your subscription.” This is a way to make sure your subscribers actually want to hear from you to ensure a higher delivery rate.
  • Reviewing your message content: If your texts are frequently not getting through to your subscribers, review your message—as well as any links or landing pages—to make sure there are no references to SHAFT, CBD, etc.
  • Getting a short code: As we mentioned earlier, short codes go through a strict approval process and, as a result, tend to be filtered less by carriers. So if you’re dealing with carrier violation-related errors, this may be an option to consider.
  • Setting up an error segment: Create a segment of SMS subscribers who are unable to receive your messages so that you can exclude them from your campaigns. This will improve your deliverability and also ensures you’re not wasting your SMS credits.

One of the challenges with any form of omnichannel marketing is figuring out how to send the right number of messages at the right times.

You want to find the right balance when texting your SMS list. Regular sends keep your brand top of mind, but sending too frequently can cause fatigue and increase opt-outs, especially if your messages aren’t personalized. The goal is to stay engaged with your audience without overwhelming them.

Even the most seasoned SMS marketers benefit from keeping these cadence best practices top of mind:

  • For SMS flows, keep SMS and MMS quiet hours enabled. This is generally any time before 9 a.m. or after 8 p.m. in the recipient’s time zone.
  • Aim to send at least 1–2 SMS campaigns per week to regularly engage subscribers.
  • If you use Klaviyo, take advantage of Smart Sending, which lets you control the number of emails, SMS messages, or push notifications someone can receive within a set period of time.

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