Mastering SMS deliverability: How to maximize SMS delivery success

Whether it’s SMS, MMS, email, or any other messaging channel, getting your messages delivered is the first and most important step in reaching your customers. According to a 2025 SimpleTexting report, 84% of U.S. consumers are opted in to receive texts from businesses, an increase of 6% from the year before. That’s great news, but those opt-ins only matter if your messages are getting through and being delivered to your customers.

High SMS deliverability not only means higher engagement, but it means stronger customer relationships, and better ROI on your SMS marketing campaigns. In this guide, we’ll break down what SMS deliverability is, why it matters, and best practices to maximize your success.

 SMS deliverability, or SMS delivery, is a metric that shows brands how many of their text messages actually reach their intended recipients. But just like email deliverability, hitting “send” doesn’t mean your marketing message will automatically appear on every phone – it has to go through several key steps first. 

So, what makes for good SMS deliverability? First and foremost, you need a list of SMS subscribers – people who have opted in to hear from you via text messaging. Otherwise, you’re just shouting into the void (or worse, being flagged as spam!).

 Not all businesses know how to gauge their SMS deliverability. At Sinch, we measure SMS deliverability as the percentage of SMS messages successfully delivered to a handset versus the number of messages submitted to our platform by the sender.

A high delivery rate means your messages are reaching recipients as expected. A lower rate signals potential deliverability issues, like carrier filtering, invalid numbers, or compliance issues.

 You’ve invested time and resources in building an engaged subscriber list, but if your texts never reach them, that effort will be wasted. Every undelivered SMS is a missed opportunity for you to connect, engage, and convert. And when it comes to transactional messages or authentication codes, the stakes are even higher; failed deliveries can mean frustrated customers, lost sales, or even security risks if users can’t complete important verifications. 

Additionally, message deliverability directly impacts:  

• Customer experience: Time-sensitive messages like one-time passwords (OTPs) or delivery notifications need to arrive pretty much instantly. If they don’t, you may experience abandonment and trust will erode fast.  

• Marketing performance: If your messages don’t reach inboxes, you give less people the opportunity to engage with you, meaning your conversions will take a hit – along with your campaign ROI. 

• Brand reputation: Sending non-compliant messages or failing to follow regulations and best practices can get your SMS traffic blocked by mobile carriers.

Source: The art and heart of meaningful customer connections, 2024 

 Achieving a 100% delivery rate isn’t realistic because there are just too many moving parts in the messaging ecosystem. Sometimes, network congestion or carrier issues cause delays that result in failed deliveries. Other times, the failure might be due to phone numbers or message formatting.  

Understanding why messages fail can help you improve your overall SMS deliverability. Here are a few common reasons texts don’t reach their final destination:  

1. Invalid or deactivated phone numbers: If a customer’s number is no longer in service or they gave you the wrong number, your message won’t be delivered. 

2. Network filters and carrier restrictions: Mobile operators may block messages they deem spammy or non-compliant. For example, if your message contains too many exclamation points or all capital letters, it might get caught in a spam filter.  

3. Unregistered or incorrect sender IDs: Some countries require sender IDs to be pre-approved and registered. This ensures messages use official routes for delivery. If your sender ID isn’t set up correctly, your message won’t make it. 

4. Poor formatting: Failing to include the correct country code or using an improper format can prevent a message from being delivered. Standard number formatting ensures your messages are rerouted correctly.  

5. Carrier congestion or downtime: During peak times like Black Friday and Cyber Monday, networks can become overloaded, leading to delays or delivery issues. Send your messages strategically to avoid these delays.

To help ensure your messages reach their destination, try a few best practices to increase your deliverability. 

If you see a low number of messages being delivered, one common issue could be that you’re using a list of incorrect or invalid phone numbers that can’t receive text messages. To help prevent this, you should implement a regular process of removing inactive numbers and use validation tools that provide number intelligence by identifying line type (mobile, landline, VoiP, etc.) of a phone number before sending messages. This process will help you ensure messages are only sent to valid mobile numbers. 

Not all SMS providers are the same. And that’s because some rely on third-party networks to deliver SMS, which means messages bounce between different third-party networks before reaching your customers. That can cause delays, delivery failures, and extra costs.  

A provider with direct carrier connections cuts out the middlemen, meaning messages travel the shortest possible route to the end consumer. At Sinch, our owned global Super Network means we have 600+ direct connections to mobile operators worldwide. This ensures your messages travel through the most efficient and compliant routes, minimizing delays and maximizing ROI for enterprise-scale campaigns.  

Because we manage our own network, we’re also faster at identifying and resolving deliverability issues. Instead of relying on third-part partners to troubleshoot with mobile operators, we work directly with MNOs, allowing us to detect potential problems sooner and resolve them more quickly. 

Some regions like the U.S. require businesses to register sender IDs, 10DLC numbers, or have their short code vetted by the CTIA and the U.S. Short Code Registry. Make sure you’re doing this to ensure compliance and help your messages avoid carrier filtering.

If a messaging service offers SMS at below-market rates, there’s a high chance that they’re using unreliable or unauthorized “grey routes.” These routes make themselves profitable by exploiting temporary pathways that can be shut off at any time, which can lead to sudden message blocking, high failure rates, or fines. Worse yet, some grey route providers charge for undelivered messages to keep prices artificially low while never actually sending the traffic. Investing in legitimate routes ensures consistent delivery and protects your brand’s reputation. 

Ensure your messages live up to carrier guidelines and specific messaging regulations like GDPR and TCPA. If your messages are being filtered or blocked, you may be violating carrier regulations or sending content that looks like spam.  

The basics? Ensure your SMS campaigns comply with local laws like proper opt-in language and avoid excessive capitalization or promotional triggers that could flag your messages as spam. And, of course, make sure to consult with your own legal team or counsel before starting any new marketing program!

Getting your messages delivered to your customers is key, but don’t forget about the everyday basics that will boost your campaign’s success. Here are a few other best practices that will help you optimize your SMS and MMS messaging campaign success:  

• Time your campaigns wisely: Schedule larger marketing campaigns well before curfew times to avoid restrictions and avoid peak hours to prevent delays. 

• Use a provider that understands your use case: If you need to send time-critical notifications (like alerts, one-time passwords, etc.), use an SMS provider optimized for speed. 

• Use short codes if possible: Short codes have strict carrier approval processes, meaning they have higher delivery rates than long codes.  

• Keep messages short and clear: Keep SMS within the 160-character limit to avoid splitting messages, which could affect readability and increase costs. If your message is longer, consider using MMS messaging (which has a 5,000-character limit with transcoding). 

• Use a double opt-in: This practice will help you ensure a higher quality list and help you avoid sending to incorrect or fake phone numbers.  

• Personalize your messages: Using customer names and other details to make the message feel relevant. This will help improve your response rate.  

• Segment your audience: Segment your contact list into relevant subgroups based on demographics like age, gender, location, customer interests, and previous buyer behavior.  

• Monitor performance: Track delivery rates and adjust your campaigns based on engagement. 

At Sinch, we take SMS deliverability seriously. Our platform ensures your messages are sent via proper gateways, and we prioritize compliance and best practices. 

When you choose Sinch, you get:  

• Over 600 direct carrier connections for reliable global message delivery 

• Compliance expertise to help you navigate messaging regulations 

• Industry-leading platform uptime and the lowest latency out there 

• Smart routing that prioritizes for cost and speed of message delivery to suit your needs

For enterprises managing large-scale messaging, SMS deliverability is mission-critical. By understanding the factors that impact message success and working with a trusted provider with enterprise-grade messaging solutions like Sinch, you can maximize your reach and engagement.  

Ready to optimize your SMS deliverability? Contact us today and see how we can help you connect with your audience more effectively.