SMS Deliverability: The Ultimate Guide to Getting Your Messages Delivered

Ever wonder why some SMS marketing messages skyrocket sales while others vanish into thin air? It’s not just about compelling copy; it’s about navigating the complex world of SMS deliverability. Many businesses invest heavily in SMS campaigns only to see their efforts wasted due to unseen roadblocks.

This guide will show you how to ensure your SMS messages actually reach your customers:

• Understand the core factors impacting SMS delivery.
• Master compliance and technical requirements.
• Implement proven strategies to boost your SMS delivery rate.

P.S. Struggling with low SMS delivery rates? Try TxtCart. Our SMS marketing platform is specifically designed to maximize deliverability rates for Shopify stores, with built-in compliance tools that help ensure your messages reach customers’ phones.

4 Key Factors Affecting SMS Deliverability

Several critical elements influence whether your SMS messages make it to your customers. Understanding these factors is the first step towards mastering SMS delivery.

#1) Carrier Filtering

Mobile carriers act as gatekeepers for SMS messages. They employ sophisticated filtering systems to protect their users from unwanted messages, spam, and fraudulent activities.

How mobile carriers evaluate and filter SMS messages

Carriers like T-Mobile, Verizon, and AT&T use algorithms to scan SMS messages for suspicious patterns. This includes looking at the sender’s phone number reputation, message content (keywords, link types), sending volume, and even user complaints.

If a message triggers these filters, it can be blocked or flagged, leading to SMS delivery failure. This process of carrier filtering is dynamic and constantly evolving.

Common triggers that cause messages to be blocked

Certain elements are notorious for triggering carrier filters. These include:

• Using public URL shorteners (like bit.ly) instead of dedicated or branded ones.
• Including prohibited content related to SHAFT (Sex, Hate, Alcohol, Firearms, Tobacco).
• Sending a high volume of identical messages in a short period (snowshoeing).
• High opt-out rates or spam complaints associated with your phone number.
• Overly promotional language or excessive use of capital letters and symbols.

Differences between major carriers’ filtering approaches

While all carriers aim to block spam and malicious content, their specific algorithms and tolerance levels can vary. Some might be more aggressive in filtering certain types of content or links. This means a message that gets through on one carrier might be blocked on another. Staying updated on general best practices is crucial as specific carrier rules can be opaque.

Technical explanation of delivery receipts and what they mean

A delivery receipt (DLR) is a notification sent back from the carrier to the SMS gateway or SMS provider, indicating the status of a sent SMS message.

• “Delivered”: The message has successfully reached the recipient’s device.
• “Undelivered”: The message could not be delivered. Reasons can include an invalid phone number, the recipient’s mobile device being off or out of service, or carrier filtering.
• “Failed”: A more general failed delivery status, often due to carrier issues or filtering.
• “Sent”: The message has been sent from the platform but a final delivery status isn’t yet available.

Understanding DLRs is vital for monitoring your SMS deliverability rate and troubleshooting delivery issues.

#2) Phone Number Types and Their Impact

Feature	Short Code	10DLC (Registered)	Toll-Free (Verified)	Traditional Long Code
Number Type	5-6 digits	10 digits	10 digits (8XX)	10 digits
Primary Use	High-volume A2P	A2P Business Messaging	A2P, Customer Service	Historically P2P, now A2P
Deliverability	Very High	High	Good to High	Low to Very Low (for A2P)
Throughput	100+ MPS	Variable (1-60+ MPS)	Variable (3-10+ MPS)	Low (1 MPS)
Cost	$$$$ (High setup & monthly)	$$ (Moderate registration)	$$ (Moderate)	$ (Low)
Filtering	Low	Moderate	Moderate	High
Voice Enabled	No	Yes	Yes	Yes
Registration	Carrier Approval	TCR Brand & Campaign	Verification Process	N/A or Carrier Approval for A2P

The type of phone number you use for sending SMS messages significantly impacts deliverability, throughput, and cost. Choosing the right one is a strategic decision.

Short codes: advantages, disadvantages, costs, and throughput rates

Short codes are 5-6 digit numbers designed for high-volume A2P (Application-to-Person) messaging.

• Advantages: Highest throughput (hundreds of messages per second), excellent deliverability when used correctly, and brand recognition. They are less likely to be filtered as spam messages by carriers.
• Disadvantages: Most expensive option (setup and monthly fees can be substantial), lengthy approval process (weeks to months).
• Costs: $500-$1500/month leasing, plus setup fees.
• Throughput: Typically 100+ MPS (Messages Per Second).

10DLC: what it is, registration requirements, and best use cases

10DLC (10-Digit Long Code) refers to a standard 10-digit phone number approved by carriers for A2P business messaging in the US.

• Advantages: Better deliverability and higher throughput than traditional long codes for business traffic, more affordable than short codes. Supports voice, so customers can receive phone calls on the same number.
• Registration Requirements: Businesses must register their brand with The Campaign Registry (TCR) to get approved throughput and reduce filtering.
• Best Use Cases: Suitable for most marketing campaigns, alerts, and customer service messaging for small to medium businesses.

Toll-free numbers: benefits for deliverability and limitations

Toll-free numbers (e.g., 800, 888, 877) can also be used for SMS marketing messages.

• Benefits: Generally decent deliverability for verified traffic, recognizable to customers, and can handle higher volumes than traditional long codes. They also support voice.
• Limitations: Throughput is typically lower than short codes but can be higher than unregistered 10DLC. Some carriers may have stricter filtering on toll-free numbers for promotional content if not properly verified. Verification processes are now common to improve trust and deliverability.

Traditional long codes: why they’re being phased out

Traditional long codes (standard 10-digit numbers not registered for A2P traffic) were once common for P2P (Person-to-Person) communication and sometimes used by businesses for smaller scale A2P.

However, carriers are actively discouraging their use for A2P SMS marketing due to widespread abuse for spam. Consequently, messages from these numbers face aggressive filtering and low deliverability rates. They are being superseded by 10DLC for business messaging.

#3) Message Content and Format

The content and structure of your SMS messages play a direct role in whether they get delivered or flagged by carrier filtering.

Character limits and their impact on deliverability

Standard SMS messages can only be up to 160 characters long if you use basic text. If you include special characters or emojis, the limit drops to 70 characters. If you exceed this, the message might be split into multiple segments.

While modern phones reassemble these, each segment counts as a separate message for billing and can sometimes face slightly higher delivery scrutiny or, in rare cases, arrive out of order. Keeping messages concise is a best practice for both cost and deliverability.

Best practices for links in SMS messages

Links are crucial for driving traffic from SMS campaigns, but they need careful handling:

• Use full domains or reputable shorteners: Avoid public URL shorteners. Opt for your own domain or shorteners provided by your SMS marketing platform.
• Ensure links lead to safe, relevant content: Links to malicious sites or irrelevant landing pages will harm your sender reputation and deliverability.
• Clearly indicate it’s a link: Don’t try to disguise links. Example, “Click here to claim your discount: www.yourbrand.com/discount” rather than hiding the link behind vague phrases like “More info.”
• Test your links: Ensure they work correctly on various devices. Test on both iOS and Android devices.

How to structure messages for maximum deliverability

A well-structured message is less likely to be flagged:

• Identify your brand: Clearly state who the message is from, especially in the first campaigns to a new recipient.
• Provide clear value: Make the purpose of the message obvious.
• Include a clear Call to Action (CTA): Tell the recipient what to do next.
• Offer an easy opt-out: E.g., “Reply STOP to unsubscribe.” This is a legal requirement and a best practice.
• Personalize (carefully): Using a customer’s name can improve engagement, but avoid overly complex personalization that might break or look suspicious.

Example text:

#4) Opt-in Quality and List Hygiene

The quality of your subscriber list and how you maintain it are foundational to SMS deliverability. Sending messages to uninterested or invalid numbers is a surefire way to encounter delivery issues.

Impact of opt-in methods on deliverability

How you collect consent (opt-in) directly affects your list quality. If customers don’t clearly understand what they’re signing up for, they are more likely to report your messages as spam, damaging your sender reputation and SMS delivery rate. Clear, explicit consent is non-negotiable.

Single vs. double opt-in comparison

• Single Opt-In: This is a one-step process. A user provides their phone number via an online form or by texting a keyword, and they are immediately added to your SMS list. It’s quick and reduces friction.

• Double Opt-In: After providing their number, the user receives a confirmation SMS and must reply (e.g., with “YES”) to confirm their subscription. This method ensures higher list quality, better engagement, and stronger proof of consent, leading to better deliverability. While it adds a step, double opt-in is highly recommended.

How to maintain a clean subscriber list

Regularly cleaning your SMS list is crucial:

• Remove inactive numbers: Periodically review your list and remove subscribers who haven’t engaged with your messages in the past 6 months. Also, consider removing numbers that consistently result in undelivered messages.
• Process opt-outs immediately: Honor all STOP requests within 24 hours to ensure compliance with regulations and maintain trust.
• Monitor for invalid numbers: Use delivery receipts and bounce-back data to identify invalid numbers that are no longer in service. Removing these numbers helps improve deliverability and reduces wasted sends

Handling inactive subscribers and error segments

For subscribers who haven’t engaged in a long time, consider a re-engagement campaign. If they don’t respond, it’s often best to remove them. For numbers that consistently produce delivery errors (e.g., “absent subscriber”), remove them from your active sending list to protect your deliverability and avoid unnecessary costs.

Here’s the SMS win-back campaign sequence with timing intervals and actions to help you re-engage customers effectively.

SMS	Time Interval	Example
“We Miss You” Message	30-45 days after inactivity	“Hey [Name], we miss you! It’s been a while since your last visit. Come back and check out what’s new!”
Highlight New Products/Offers	3-7 days after SMS 1	“Hi [Name], we’ve got some exciting new products just for you! Enjoy 20% off your purchase.”
Urgency + Request for Feedback	3-7 days after SMS 2	“We’d love to know how we can improve! Please share why you haven’t returned yet—your feedback helps us get better. P.S. Your 20% off is still available!”
Last Chance Reminder	5-7 days after SMS 3	“Last chance! Don’t miss your 20% off—grab it before it’s gone! We’d love to have you back.”

Thinking about how to win back those quiet subscribers? TxtCart empowers you to launch effective re-engagement campaigns. For instance, you can use our Smart Segmentation to identify customers who haven’t purchased in, say, 30-45 days, and then send them a special “We Miss You!” offer.

Read Next:

• The Complete SMS Opt-in Playbook for 2025: Tips & Examples
• 15 Ways to Grow Your SMS List (No One Talks About #3)
• SMS List Cleaning: Why Is It Important and How to Do It for Your Shopify Store

Compliance Requirements for SMS Deliverability

Adhering to legal and industry regulations is not just a best practice for SMS deliverability; it’s a necessity to avoid hefty fines and maintain a good sender reputation with carriers.

TCPA Compliance

The Telephone Consumer Protection Act (TCPA) is a U.S. federal law that governs telemarketing calls, auto-dialed calls, pre-recorded messages, and text messages. Understanding and complying with TCPA is critical for any business sending SMS messages to U.S. consumers.

Explicit consent requirements

Under the TCPA, you must obtain express written consent from individuals before sending them marketing SMS. This consent must be unambiguous, meaning the person clearly understands they are agreeing to receive marketing messages via SMS from your brand.

• The disclosure must be clear and conspicuous.
• Consent cannot be a condition of purchase.
• Records of this consent must be kept.

Record-keeping best practices

Maintain thorough records of consent for every subscriber. This includes:

• The phone number that opted in.
• The date and time of the opt-in.
• The specific disclosure language presented at the time of opt-in.
• The source of the opt-in (e.g., web form, keyword text-in). These records are your defense if a complaint arises.

CTIA Guidelines

The CTIA (Cellular Telecommunications Industry Association) represents the U.S. wireless communications industry. While not law, their guidelines are considered industry best practices and are enforced by mobile carriers. Non-compliance can lead to carrier violation flags and your messages being blocked.

Industry best practices for SMS messaging

CTIA guidelines reinforce many TCPA principles and add others:

• Clear opt-in: Ensure consumers knowingly consent to receive messages.
• Clear opt-out: Provide a simple and consistent way for consumers to revoke consent (e.g., replying STOP).
• Message frequency disclosure: Inform users how often they can expect messages.
• Help information: Provide a way for users to get help (e.g., reply HELP for info).
• Content restrictions: Particularly around SHAFT.

Opt-out requirements

You must provide a clear, free, and easy way for recipients to opt out of future messages. The standard method is replying “STOP.” This request must be honored immediately and universally across all your SMS campaigns for that phone number. Other keywords like “UNSUBSCRIBE,” “CANCEL,” or “QUIT” should also be recognized.

P.S. TxtCart’s Scheduler allows you to send messages according to each subscriber’s timezone. This ensures you never disturb customers at inappropriate hours, helping maintain compliance and positive customer relationships, which contribute to high SMS delivery rates.

For most eCommerce brands, sending 1-2 promotional SMS campaigns per week is a good starting point. Sending too frequently can lead to annoyance, opt-outs, and spam complaints, harming your deliverability. Transactional messages (order confirmations, shipping updates) are an exception and should be sent as needed.

Read Next:

• SMS Marketing Compliance 101: A Guide For Shopify Businesses
• TCPA Compliance Guide for SMS Marketing [+ Checklist]

Technical Aspects of SMS Deliverability

Beyond content and compliance, the underlying technology of how SMS messages are sent and received plays a significant role in deliverability.

SMS Infrastructure

Understanding the journey of an SMS message helps in appreciating the technical nuances affecting its delivery.

How SMS messages are routed through carriers

When you send messages via an SMS provider, it doesn’t go directly to the recipient’s phone. It first goes to an SMS gateway, which then routes it through a complex network of mobile carrier systems (like SS7 signaling networks) to the recipient’s mobile device. Each hop in this journey can introduce potential points of failure or filtering.

Technical differences from email delivery

Email delivery relies on SMTP servers, DNS records (MX, SPF, DKIM, DMARC), and IP reputation. SMS delivery is more dependent on the phone number’s reputation (e.g., short code vs. 10DLC), direct carrier relationships, and the specific protocols used by SMS gateways and aggregators. Filtering is often more immediate and less forgiving in SMS.

Role of aggregators in the delivery process

Aggregators are entities that have direct connections to multiple mobile carriers. SMS providers often work with aggregators to send and receive SMS messages at scale. The quality and connections of the aggregator used by your SMS provider can significantly impact your SMS delivery rate and reliability.

Delivery receipts and what they tell you

As discussed earlier, delivery receipts (DLRs) are crucial technical feedback. They indicate if a message was delivered, failed, or is pending. Analyzing DLRs helps identify issues like invalid numbers, carrier filtering, or problems with the recipient’s device. They are essential for calculating your true SMS deliverability rate.

Measuring and Improving SMS Deliverability

You can’t improve what you don’t measure. Actively monitoring key metrics and systematically addressing issues are vital for maintaining high SMS delivery rates.

Key Metrics to Track

Tracking these metrics will give you insights into your SMS deliverability performance and help you identify areas for improvement in your SMS campaigns.

Metric	Calculation	Improvement Strategies
Delivery Rate	(Delivered Messages ÷ Total Sent) × 100	Run monthly list hygiene by exporting all numbers that returned “invalid” or “absent subscriber” errors and removing them immediately. If using long codes, migrate to a registered 10DLC number which can handle higher volumes without triggering carrier blocks. Contact your SMS provider within 24 hours of any delivery rate drop to check if specific carriers are blocking your traffic.
Failure Rate	(Failed Messages ÷ Total Sent) × 100	Numbers returning “invalid” errors should be removed within 48 hours to prevent further delivery issues. For “blocked” or “filtered” errors, review your message content from the past 7 days for compliance violations, then test revised content on a 100-person segment before resuming full campaigns.
Click-Through Rate	(Clicks ÷ Delivered Messages) × 100	A/B test different offers and CTA like “Free delivery” vs “Get 20% off now”. Personalize messages with the subscriber’s first name and recent browsing data. Replace generic bit.ly links with branded short domains. Test different send times.
Conversion Rate	(Conversions ÷ Delivered Messages) × 100	Create unique promo codes for each SMS campaign. Add UTM parameters to all links. Ensure your landing pages load in under 3 seconds on mobile and match the offer mentioned in your SMS exactly. Set up automated follow-up sequences to re-engage non-converters within 48 hours with a different angle or stronger incentive.
Opt-Out Rate	(Opt-outs ÷ Delivered Messages) × 100	Segment your list by purchase history and engagement level, sending your best offers only to VIP customers while using gentler messaging for new subscribers. If opt-out rates exceed 3% for two consecutive campaigns, immediately reduce sending frequency from daily to 2-3 times per week. Send a brief survey to recent opt-outs to identify content issues. Create a preference center where subscribers can choose message frequency.

A/B Testing for Deliverability

Systematic A/B testing can help you fine-tune your SMS campaigns for optimal deliverability and engagement.

Testing message content variations

Test different:

• Calls to Action (CTAs).
• Promotional offers or language.
• Use of emojis or special characters.
• Message length.

Send Version A to one segment and Version B to another, then compare delivery rates and engagement.

Optimizing send times

Experiment with sending SMS messages at different times of the day or days of the week (while always respecting quiet hours). Track delivery rates and response rates to find the sweet spot for your audience. The optimal delivery time can significantly impact engagement.

Experimenting with different number types

If feasible and you’re experiencing persistent deliverability issues, you might test sending from a different phone number type (e.g., trying a 10DLC if you’re using a Toll-Free Number for certain types of campaigns, or vice-versa). This is a more significant change and should be based on thorough analysis.

Measuring the impact on deliverability

For every A/B test, the primary metric for deliverability is the SMS delivery rate. Also, monitor secondary metrics like failure rates, opt-out rates, and engagement (CTR, conversions) as these can provide a more holistic view of message effectiveness and reception.

P.S. TxtCart’s Campaign & Revenue Analytics tracks delivery rates and engagement metrics in real-time, helping you spot deliverability issues before they impact your sender reputation.

The platform also simplifies A/B testing for deliverability optimization—test different message formats, send times, and CTAs while monitoring how each variation affects your delivery success.

Read Next:

• SMS Marketing Analytics: 10 SMS Metrics You Cannot Ignore
• SMS A/B Testing: 15 Types of SMS Tests & Examples

Unlock High SMS Deliverability with TxtCart

You’ve now journeyed through the intricacies of SMS deliverability, from understanding carrier filtering to mastering compliance. Armed with this knowledge, you’re ready to ensure your SMS messages don’t just get sent, they get seen. Here’s what to remember:

• Prioritize consent and list hygiene: A clean, engaged list is your best defense against delivery issues.
• Content and compliance are king: Craft clear, valuable messages that respect regulations and recipient preferences.
• Monitor and adapt: Continuously track your SMS delivery rate and other metrics, and be ready to adjust your strategy.
• Choose the right tools: Your phone number type and SMS provider significantly impact success.

Now that you understand how to get your SMS messages delivered, it’s time to make every message count. TxtCart provides the platform and expertise to not only achieve high SMS delivery rates but also to convert those delivered messages into loyal customers and increased revenue.