Improving SMS Deliverability when Using Long Numbers

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Wireless carriers, including AT&T, Verizon, T-Mobile, and Sprint, monitor SMS sent over their networks to prevent the delivery of spam. When messages are sent from a 10-digit long number, carriers will sometimes filter out texts that their systems have flagged. One way to improve deliverability is by using several sending numbers to avoid having all the volume and traffic come through one number. This article will share how many long numbers you should have and how to add them.

Recommended Number of Long Codes

The number of long numbers an account should have is based on how many SMS subscribers you have. A best practice is to have one long code per every 200 SMS subscribers that you send to regularly.

SMS Subscriber Volume Recommended Number of Long Codes
<200 1
201–400 2
401–600 3
601–800 4
801–1,000 5
1001–1200 6
1,401–1,600 8
1,601–1,800 9
1,801–2,000 10

Adding Long Codes to Your Account

You can add up to 20 long codes to your account. (If you need more than 20 long numbers, please contact Klaviyo Support and we can add more.) From your dashboard, click your organization name in the upper right-hand corner. Then, click Account > Settings > SMS Settings. The first section in that page is the Sending Numbers section. There, select the Additional Numbers dropdown and click Request Additional Numbers


Note that each new long code you request comes with a subscription fee of $1/month.

Using the New Numbers

Klaviyo uses “sticky sending,” which means that a recipient will always receive communications from the same phone number. When you add new long codes, you can request to have your phone numbers evenly distributed among your SMS subscribers. To do this, please contact our Support team. Note that when you request this change, some recipients will see a shift in the number from which they receive SMS from your brand.

Additional Resources

Check out these articles to learn more about SMS deliverability:


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