SMS vs Email for Post-Purchase Upsells: Which Converts Better?

The Channel Battle

After a customer makes a purchase, you have a golden opportunity to increase their order value with additional offers. But which channel should you use—SMS or email?

Both have their strengths. Email is familiar and cost-effective. SMS is immediate and impossible to ignore. Let's look at what the data says.

Side-by-Side Comparison

Sources: Omnisend^[1], Mailmodo^[2], WebFX^[3]

Open Rates: SMS Dominates

SMS achieves open rates of 90-98%—almost every message gets read^[1]. Email, by contrast, averages 20-28% open rates.

Why the massive difference?

• SMS notifications are harder to ignore

  They appear on the lock screen and trigger immediate attention

• No spam folder

  SMS messages arrive directly in the inbox without filtering

• Fewer messages

  People receive fewer texts than emails, so each stands out more

• Personal device

  Phones are always within reach, typically checked within minutes

Time to Open

90% of SMS messages are read within 3 minutes^[4]. Email responses take an average of 90 minutes—and many are never opened at all.

Conversion Rates: SMS Wins Again

For post-purchase upsells specifically:

• SMS: 21-40% average conversion rate^[1]
• Email: 9-15% conversion rate^[5]

Post-Purchase Email Stats

Post-purchase emails do perform better than regular promotional emails^[5]:

• 217% higher open rates than standard emails
• Upsell emails: 61.7% open rate, 9.16% conversion rate
• Cart abandonment emails: 44.76% open rate, ~7% conversion

SMS Cart Recovery

For abandoned cart recovery, SMS converts at 24.6-39.4%, while email converts around 7%^[6]. That's 3-5x higher conversion for SMS.

ROI Comparison

Both channels deliver strong returns, but SMS edges ahead (see our detailed SMS ROI statistics for more data):

• SMS: $45-71 return per $1 spent (up to 7,100% ROI)^[3]
• Email: $36-42 return per $1 spent (3,600-4,200% ROI)^[7]

The higher ROI for SMS comes from better engagement metrics. Even though SMS costs more per message, the conversion rates more than compensate.

Timing & Response Speed

SMS is designed for immediacy:

• Average response time: 90 seconds
• 90% read within 3 minutes
• Ideal for time-sensitive offers

Email is better for less urgent communication:

• Average response time: 90 minutes
• Often batch-checked 2-3 times per day
• Better for detailed content customers can review later

For Post-Purchase Upsells

The immediacy of SMS is valuable for post-purchase moments when customers are excited about their order. A text saying "Thanks for your order! Add this matching item for 20% off" arrives while the purchase is still fresh.

Cost Comparison

Email is significantly cheaper per message^[2]:

• Email: $0.001-0.003 per message
• SMS: $0.01-0.05 per message

Example: 10,000 Messages

SMS costs more upfront but delivers 5-10x more conversions. If your average upsell value is $25, SMS generates $52,500-97,500 in revenue vs email's $4,500-10,500—easily justifying the higher per-message cost.

When to Use SMS for Upsells

SMS excels in these scenarios:

• Time-Sensitive Offers

  "Your 20% off expires in 2 hours" – SMS ensures they see it in time

• Post-Purchase Follow-Up

  Reaching customers right after purchase, when excitement is high. This is exactly what Upsella is built for.

• Order Updates + Upsells

  "Your order shipped! While you wait, here's a special offer..."

• High-Value Customers

  VIP customers who warrant the higher per-message cost

• Cart Abandonment Recovery

  When someone leaves items in their cart, SMS gets their attention faster

When to Use Email for Upsells

Email is better for:

• Detailed Product Information

  When the upsell requires explanation, images, or comparison charts

• Long-Form Content

  Educational content about complementary products, how-to guides, etc.

• Large Subscriber Lists

  When cost is a primary concern and you're messaging thousands of people

• Non-Urgent Follow-Ups

  Product recommendations days or weeks after purchase

• Customers Who Prefer Email

  Some customers don't want text messages from brands. Respect their preference.

The Best Approach: Use Both Strategically

The data is clear: SMS outperforms email for engagement and conversion. But the optimal strategy isn't choosing one—it's using both where they're strongest^[3].

Recommended Strategy

Key Principle

SMS for urgency and attention. Email for depth and detail.

Customers tolerate daily emails but not daily texts^[2]. Use SMS sparingly for high-impact moments; use email for regular communication.

How Upsella Fits In

Upsella handles the SMS side automatically:

• AI analyzes each purchase to recommend relevant products
• Messages sent at optimal moments (checkout, shipping, delivery)
• One-tap purchase links for frictionless buying
• Runs independently once configured

Pair Upsella with your existing email flows for a complete post-purchase strategy.

See how Upsella works

Frequently Asked Questions

Is SMS or email better for post-purchase upsells?

SMS outperforms email: 98% open rate vs 20%, 21-40% conversion vs 9-15%, $71 ROI per $1 vs $36-42. For immediate, time-sensitive offers, SMS wins. For detailed product information, email is better.

How fast do people respond to SMS vs email?

SMS average response time is 90 seconds. Email average is 90 minutes. 90% of SMS messages are read within 3 minutes.

Is SMS marketing more expensive than email?

Per message, yes: SMS costs $0.01-0.05 vs $0.001-0.003 for email. But SMS delivers 5-10x more conversions, so cost per conversion is often lower with SMS.

Should I use both SMS and email?

Yes. Use SMS for immediate high-impact moments (post-purchase, shipping updates, delivery). Use email for detailed content, product guides, and long-term nurturing. The best results come from combining both strategically.

How many texts per month is acceptable?

Customers tolerate 2-4 SMS messages per month. More than that leads to unsubscribes. Reserve SMS for your most important, time-sensitive offers.

Conclusion

The numbers don't lie: SMS dramatically outperforms email for engagement and conversion. With 98% open rates, 21-40% conversion rates, and 60x faster response times, SMS is the superior channel for time-sensitive post-purchase upsells.

Key takeaways:

• SMS: 98% open rate vs email's 20%
• SMS: 21-40% conversion vs email's 9-15%
• SMS: $71 ROI per $1 vs email's $36-42
• Use SMS for immediate post-purchase moments
• Use email for detailed content and long-term nurturing
• The best results come from combining both strategically

For post-purchase upselling specifically, Upsella's AI-powered SMS delivers the immediacy and personalization that drives conversions. Start your free trial to see the difference.