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:

• 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

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.