Understanding the difference between email and SMS

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Learn how email and SMS differ as as well as when to use each channel. 

When to use SMS vs. email


Use a text message when you want to make sure a message is seen quickly; for instance, when the content is time-sensitive (e.g., flash sale) or extremely important (e.g., store opening/closing). Further, SMS is useful for sending order updates or delivery confirmations, as your customers will know exactly when to expect their package and when they can go and get it. Other examples where an SMS might outperform email include your initial welcome message and general sale announcements. 

Treat your SMS subscribers similar to your VIPs; they are your brand enthusiasts who will advocate for you. Thus be included in any special offers (e.g., early access or deals) and surveys directed at your most dedicated customers. 


Use an email for longer-form content, including newsletters, and any messages that you want to reach everyone in your audience, such as a product announcement. 

Send any important messages you sent by SMS via email to the rest of your subscribers. The only exceptions are if you're sending an exclusive offer to SMS subscribers or are asking for feedback from this group in particular. 


Your base plan in Klaviyo includes all profiles for your account as well as the ability to send emails. SMS is a separate, add-on plan that only deals with the number of credits you want. 

For more information about these plans, see this article on how Klaviyo billing works for email and SMS.

Consent and spam

Collecting consent

Email and SMS consent are treated separately:

  • Consent for email does not count as consent for SMS and vice versa.
  • SMS consent must be collected separately from email (e.g., you can't use a checkbox to say someone agrees to both email and SMS).

Regardless of the type of communication, it’s crucial that you have the proper permissions to message customers before contacting them. However, while you can get email consent implicitly in some cases, consent for SMS marketing must always be explicit. 

How spam is treated

If someone happens to mark your emails as spam, this will impact your sending to that recipient and also hurt your inbox provider reputation.

When it comes to SMS, if someone reports you as spam to their phone carrier, you will be hit with a fine. For more information, head to this section on localized compliance laws.  


Email is available anywhere in the world. However, you can only send SMS messages to recipients in certain countries.

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 and send to only those profiles.

Identifying your brand

When receiving an email, a recipient can look at the sender and sender email address in their inbox to know who is sending the message.

Except in the UK and Australia, where the sender ID can be customized, 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 (US only) so customers will know who is texting them.

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.

The default conversion windows are:

  • 5 days for email 
  • 24 hours for SMS

However, you can adjust these windows. For instructions, 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. 

All SMS messages in Klaviyo require consent, including those with transactional content. Due to this, there is no transactional status for SMS messages in Klaviyo. 

With email, you have an option to choose whether recipients who recently received an email will be skipped due to Smart Sending or if they should still receive transactional messages. For more information on Smart Sending, head to our article on Smart Sending in Klaviyo.


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.

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