SMS vs. Email Follow-Up: Open Rates, Response Rates, Revenue

"Should I follow up with my leads over SMS or email?"

The honest answer is: yes. Both. In the right order, at the right times, for the right reasons. Picking one channel and ignoring the other is the kind of thinking that made sense in 2015.

But if you want the numbers that prove it — here they are.

What are the real open rates for SMS vs. email?

SMS open rates hit roughly 98% according to Gartner and industry consensus; email open rates average 21% across industries per HubSpot and Campaign Monitor benchmarks. That's not close. That's a different universe.

The open rate gap is the single most-cited stat in all of lead follow-up, and it holds up across dozens of studies. Why? Because SMS hits a phone that's already in the prospect's hand, triggers a push notification, and has no spam filter in front of it. Email gets fought over by a dozen other senders, a promotions tab, and a "inbox zero" reflex that treats most mail as noise.

This is the same dynamic we broke down in AI SMS Follow-Up: How It Works — the channel itself is the advantage.

What about response rates?

SMS response rates on personalized, transactional messages run 30–45% in lead follow-up contexts. Email response rates typically land in the 6–10% range. SMS doesn't just get opened more — it gets replied to more.

Why the gap widens:

• SMS feels personal. A text from a business is rarer than an email, so it carries more weight. Prospects reply like they would to a friend.
• Reply friction is lower. Typing a three-word SMS reply is effortless. Composing an email reply triggers a "I'll get to this later" instinct.
• SMS is synchronous. The prospect reads your message, they're already holding their phone, and the reply happens in seconds. Email is asynchronous by design.

That said, email can win on total responses when you factor in volume. You can send 10 emails for the cost and compliance overhead of 1 SMS. If each email pulls a 7% response rate, 10 emails pull ~52% cumulative response — competitive with SMS at a fraction of the effort.

The trick is recognizing which metric matters in which context: SMS for single-touch urgency, email for aggregate volume.

Which one is cheaper?

Email is roughly 10–100x cheaper per send than SMS in the US. That matters at scale; it's a rounding error for transactional lead follow-up.

Ballpark costs:

• Email: $0.0001 to $0.001 per send depending on platform (SendGrid, Mailgun, native CRM). Plus platform monthly fees.
• SMS (US): $0.007 to $0.015 per send, plus 10DLC carrier fees ($2–$10 per 1,000 messages) and brand/campaign registration.
• MMS (SMS with media): Roughly 2–3x the cost of plain SMS.

For a business doing 500 lead follow-ups a month, SMS costs $15–$30 in message fees. Email costs under $1. The SMS premium buys you 5x the open rate and 4x the response rate. Math is easy.

At 50,000 messages a month, the costs get more interesting — that's when big brands start rationing SMS for the highest-priority touches. For a small-to-mid sized business running lead follow-up, you don't hit that scale.

How do the compliance rules compare?

SMS has the stricter compliance bar thanks to TCPA; email is governed by CAN-SPAM, which is less onerous but still enforced. Both are manageable with standard practices.

SMS (TCPA + 10DLC):

• Prior express written consent required for marketing messages
• Clear opt-out (reply STOP) in every message thread
• Quiet hours: no sends before 8am or after 9pm local time
• 10DLC brand and campaign registration for US carriers (The Campaign Registry)
• Penalties: $500 to $1,500 per violating message under TCPA

Email (CAN-SPAM):

• Accurate "From," "Reply-To," and routing information
• Non-deceptive subject lines that reflect the content
• Clear identification as an advertisement if applicable
• Physical mailing address in every email
• Functional unsubscribe honored within 10 business days
• Penalties: up to $51,744 per violation (inflation-adjusted)

CAN-SPAM is looser than TCPA, which is why you get so many marketing emails and so many fewer unsolicited texts. But both regimes exist for good reasons, and the platforms that enforce them (Gmail, Yahoo, major US carriers) are getting more aggressive every year about blocking bad actors.

When should I use SMS vs. email?

Use SMS when time-to-read matters; use email when content depth matters. That's the rule, and 90% of the channel decision comes down to it.

SMS is the right call for:

• Instant response to a new lead (see Speed to Lead: Why the First 5 Minutes Make or Break Your Sale)
• Appointment confirmations and reminders
• Urgent nudges ("Still want that quote? Reply YES")
• Missed-call text-back
• Short, high-intent questions that need a quick yes/no answer

Email is the right call for:

• Educational content (guides, case studies, webinar links)
• Detailed offers that need formatting, images, or multiple sections
• Long-running nurture sequences (see Lead Nurture Email Sequences That Work)
• Cold outbound where SMS would violate TCPA consent
• Re-engagement of stale leads where a text would feel intrusive

SMS is a tap on the shoulder. Email is a letter in the mailbox. Both have their moments. Neither one can do the other's job well.

What does the combined cadence look like?

The highest-performing follow-up cadences use SMS and email in parallel, hitting different cognitive modes at different moments. Running both typically lifts total response rates 40%+ over either channel alone.

Sample 10-day cadence for a service business:

• T + 30 sec: SMS. "Hi [Name] — got your request. Can I call you at [phone]?"
• T + 5 min: Email. Welcome note + link to a relevant case study or guide.
• T + 1 hr (if no reply): SMS. "Still want to chat? Here's my calendar: [link]"
• Day 1: Email. Detailed value prop + second case study.
• Day 2: SMS. Short nudge referencing the lead's original interest.
• Day 3: Email. Objection-handler or FAQ piece.
• Day 5: SMS. "Is this still a priority? If not, I'll stop bugging you."
• Day 7: Email. Social proof + direct ask.
• Day 10: SMS. "Final follow-up — reply YES if you want to reconnect, otherwise I'll assume not a fit."

That cadence aligns with the 5-to-12 touch rule documented in The 5-to-12 Touch Rule. Nine touches, two channels, no spam. Prospects who don't respond by day 10 go into a long-term nurture where email does the heavy lifting and SMS only fires on behavior triggers (link clicks, calendar views, return site visits).

For why so many sales reps quit before the cadence is complete, see The Follow-Up Gap: Why Salespeople Quit After One Attempt.

What about deliverability?

SMS deliverability is near-100% when compliance is clean and the number is registered with 10DLC. Email deliverability is an arms race — Gmail, Yahoo, and Apple Mail all tightened sender requirements in 2024 and 2025. Authentication (SPF, DKIM, DMARC) is no longer optional; it's the cost of landing in an inbox.

Practical hygiene:

• Authenticate every sending domain (SPF, DKIM, DMARC — all three)
• Warm up new sending domains slowly (start at 50 sends/day, ramp)
• Clean your email list quarterly — bounces tank reputation
• Register SMS numbers through 10DLC (or use a toll-free number for lower-volume use cases)
• Monitor carrier feedback and unsubscribe rates — they're the leading indicator of trouble

If your emails aren't landing in the inbox, no open rate stat in the world helps you. Deliverability is the precondition for everything else.

You don't have an open rate problem. You have a deliverability problem wearing an open rate costume.

Which should I deploy first?

SMS. Every time.

If you're starting from zero, instant SMS on form submit is the highest-ROI automation in the entire follow-up stack. It works in 15 seconds, doesn't require a CRM overhaul, and lifts contact rates more than any other single change. Email sequences are powerful, but they take weeks to build, test, and optimize — and they'll never match the raw engagement of a text sent at the right moment.

Build SMS first. Layer email on top. Then let both run in the same cadence, on every lead, forever.

The channel doesn't close the deal. The cadence does. Pick both. Build the rhythm. Stop losing leads to the gap between "they filled out the form" and "someone actually followed up."