SMS deliverability: Tips to reach every phone 

SMS is one of the most powerful and personal channels in your marketing toolkit. With 98% open rates and 95% of texts read within 3 minutes,* it gives you an unmatched opportunity to reach your audience quickly.

But with great power comes great responsibility. Carriers enforce strict rules to protect consumers from spam and abuse. If you don’t follow best practices, your messages can be filtered, delayed, or even blocked—and in some cases, you could face legal penalties.

Deliverability is about more than just technology. It’s about ensuring your texts are trusted, compliant, and effective.

SMS feels more personal than email, so timing and frequency matter. Avoid late-night or early-morning messages, and focus on “high-value” communications that customers expect.

• Baseline: ~1 marketing text per week (≈ 4/month).
• Normal range: 2–6 texts/month, depending on seasonality and campaigns.
• Upper caution threshold: More than 6–10 texts/month risks fatigue and higher opt-outs.
• Carrier note: CTIA and U.S. carriers recommend sending at least one message/month with opt-out/help instructions. This isn’t a law, but it’s a best practice to avoid compliance issues.
• Iterate & adapt: Test, monitor engagement, and adjust frequency based on customer response.

Tip: In the U.S., the TCPA restricts marketing texts to 8 a.m.–9 p.m. local time. To stay compliant, always check local laws like GDPR (EU) and CASL (Canada).

Carriers are quick to flag messages that look spammy. Avoid ALL CAPS, overusing punctuation (!!!), or sending vague promotions.

Instead, keep your SMS simple, professional, and actionable.

Example:

❌ “!!!! BIG SALE TODAY !!!!”

✅ “Hi Sarah, save 20% today only. Shop here: [link]”

A little personalization goes a long way. Start messages with your brand name, and include the customer’s name when you can. This builds trust and signals legitimacy to both carriers and recipients.

Brands doing it well often combine:

• Clear brand identity at the start of the message
• Customized URLs/domains
• Personalized details (like a name or location)
• Clean, professional language

Carriers watch for suspicious spikes. Like email, they prefer consistent, predictable sending patterns. Your sender type—10DLC, toll-free, or short code—comes with strict throughput caps that you’ll need to respect.

Best practices:

• Avoid blasting huge lists all at once.
• Stay within your registered sender’s per-minute and daily limits.
• High-volume vetted senders (e.g., short codes) can handle 100K+ per day, but you should still scale thoughtfully.
• If you’re increasing your daily volume (e.g., 20K → 100K), warm up gradually.
• Spread very large sends (50K+) across a few hours or days to reduce risk.

Deliverability isn’t “set it and forget it.” Track delivery reports for invalid numbers, carrier filtering, and error spikes. Continuously sending to bad numbers can damage your sender reputation—just like it does with email.

Just as importantly:

• Always honor opt-outs immediately.
• Keep a clear record of both opt-ins and opt-outs.
• Only send to customers who have explicitly consented.

Pro tip: Set expectations up front in your opt-in language. This transparency builds trust and helps you stay compliant.

Don’t skip this step. Carriers often require registration for short codes, toll-free numbers, or 10DLC in the U.S. Using unregistered or shared numbers increases the risk of blocking or filtering.

Links are a trust signal. Free or generic shorteners like bit.ly are often flagged as spam. Use branded or dedicated domains for links whenever possible.

Many carriers block messages in restricted categories (commonly referred to as SHAFT):

• Sex
• Hate
• Alcohol
• Firearms
• Tobacco
• Cannabis (including CBD) is prohibited in certain regions

Always check local regulations and carrier rules (like CTIA in the U.S.) before sending.

At Customer.io, we make SMS deliverability easier by baking compliance and best practices directly into the platform.

With us, you’ll get:

• Automatic opt-out handling and compliance tools
• Help with sender registration (10DLC, toll-free, or short code)
• Smart sending controls for timing and pacing
• Real-time insights and data-driven segmentation to keep your lists clean
• Automatic branded link shortening for trusted URLs
• Expert strategy and technical support to keep your SMS program effective

Deliverability isn’t just about technology; it’s all about trust. When your messages are timely, personal, and valuable, customers engage, carriers deliver, and long-term relationships thrive. Respect your customers’ attention, and you’ll build stronger, lasting connections.