The Difference Between SMS and Email

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Email and SMS are powerful communication tools that you can use to build relationships with your customers and drive conversions. While email and SMS are both ways to communicate with your customers, they are different in a handful of ways. This article will help you understand where email and SMS differ and point you to resources for both.

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While both sets of messages are billed monthly, how Klaviyo bills you for email and SMS is different. Email is billed monthly, based on how many profiles and email sends you have within a particular month. If you go over your limit, you’ll have the option to upgrade.

With SMS and MMS, the only thing you’ll be billed on a monthly basis is your phone number if you have more than the one free long code, a toll-free number, or a short code. Further, SMS and MMS messages are priced differently: $0.01 and $0.03, respectively. After the free $1.50 that you receive upon SMS setup, you can load a balance to your Klaviyo account.

Once your balance drops below the price of a message, your SMS messages will be skipped in campaigns and flows. You can set up automatic refill for an experience more similar to email billing.

Consent and Spam

Regardless of the type of communication, it’s crucial that you have the proper permissions to message customers before contacting them. With email, this looks like allowing a subscriber to opt in either by signup form or at check out. Additionally, you can have double opt-in enabled to ensure you’re not sending to spam traps. If someone happens to mark your emails as spam, this will impact your sending to that recipient and also hurt your inbox provider reputation.

With SMS, the consent process is mostly the same, but spam complaints are handled differently. Just like with email, you can collect subscribers’ consent through a signup form — either click to text or through entering their information. In addition, customers can click to text through email or text JOIN to your SMS number to give SMS consent.

Unlike email, however, if someone reports you as spam to their phone carrier, you will be hit with a fine. For more information, head to our article on US SMS Compliance Laws

Communication with Non-US Customers

Currently, you can only send SMS messages to US numbers. If you’re both emailing and sending SMS messages within a flow, you can split the flow based on someone’s SMS consent at the beginning of the flow in order to maintain different experiences for your SMS opted in customers and those who have not. For campaigns, you can create a segment of SMS subscribers in the U.S. and send to only those profiles.

Identifying Your Brand

When receiving an email, a recipient can look at the from/reply-to address in their inbox to know who is sending the message. Unlike email, someone receiving an SMS message will have no idea who your brand is unless you identify yourself. You’ll need to introduce your brand in the copy of your SMS or turn on the organization prefix so customers will know who is texting them.


A/B Testing

When building out your flow messages, you can always A/B test the type of message, time delay, or content of the message by using a conditional split that separates recipients by a random sample.


With emails alone, however, you can A/B test the content of the email by A/B testing that specific email. For more information on A/B testing for emails in flows, check out our article on A/B Testing a Flow. If you’re looking for inspiration for A/B testing both emails and SMS messages in your flows, head to our article on Testing SMS Messages in Flows

You cannot currently use A/B testing for SMS campaigns. 

Conversion Tracking

When a customer follows through with their purchase, Klaviyo records the message that pushed them to convert. Klaviyo knows where to attribute the purchase through your conversion windows. You can set the conversion window to whatever time delay makes sense for your brand but by default, the email and SMS conversion periods are five days and 24 hours, respectively. If you want step-by-step instructions changing these settings, head to our article on Conversion Tracking.

When creating your flows and campaigns, you should check that your conversion window from one message won’t impact the other. For example, if you have an abandoned cart email that goes out two days before an SMS message is sent, and a customer converts on the SMS message, it will be attributed to email. For a flow that has both email and SMS messages, the best way to keep this from happening is to put SMS messages before the emails. When it comes to campaigns, consider sending SMS campaigns before email campaigns if they deal with the same topic. 

Transactional Messaging

You can send both email and SMS messages to keep customers updated with their recent purchases. Transactional SMS messages will send regardless of your smart sending settings. With email, however, if you have Smart Sending turned on for your transactional messages, and a customer has received an email recently, they will be skipped. For more information on Smart Sending, head to our article on Smart Sending for Flows.


Both email and SMS have associated metrics that correspond to customer actions with your brand. You can use these metrics to gain business insights, trigger flows, or personalize communication with your customers. Head to our articles on Email Metrics and SMS Metrics for the corresponding metrics within your account.

UTM Tracking

UTM tracking allows you to pull your data into Google Analytics to measure your marketing performance. With email, you can create UTM parameters within Klaviyo both for your flows and campaigns. For SMS, you will have to create your UTM parameters within Google Analytics and include them in your SMS links. For more information, head to our article on UTM Tracking in Klaviyo

Graphic of Email vs. SMS


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