SMS delivery process

Knowing how SMS is delivered can optimize your SMS campaigns. Here's a brief overview of how a message travels from initiation to delivery or potential blockage:

1. Message sent: The sender’s platform creates and sends the SMS.
2. Message routed: The SMS gateway receives the message and directs it to the appropriate mobile carrier. This step involves passing through various network gateways, and possibly different carriers if the sender and recipient are on different networks.‍
3. Carrier processing:

          👉 The carrier checks network availability and the recipient's status to determine if it can deliver the message.

           👉 If approved, the carrier delivers the message to the recipient’s device.

           👉 If flagged, the carrier filters or blocks the message, preventing delivery.

1. Carrier filtering

Most mobile carriers actively prevent spam by filtering messages that show suspicious patterns. These filters analyze the sender's behavior, such as message frequency and the consistency of volume over time.

For example, a sudden spike in message volume from a new number may trigger carrier filters to block those messages, interpreting them as potential spam.

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2. Message content

The actual text of your messages can trigger spam filters if they contain certain keywords or phrases typically associated with spam. Messages that include phrases like "You've won!" or "Claim your prize now!" are more likely to be flagged as spam.

Additionally, messages that include shady links or that do not comply with formatting rules (like including non-standard characters) are more likely to be filtered.

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4. Network issues

Factors such as network reliability during high traffic periods or technical failures can hinder SMS delivery success beyond content and reputation. 

Similarly, if the recipient's phone is off, out of range, or has inbox storage issues, these problems must be resolved before the message can be delivered.

For example, during natural disasters, networks may become congested, leading to higher rates of undelivered messages.

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5. Regulatory compliance

Regulations around SMS messaging vary significantly by region and country with local and international laws. Most regions have Do Not Disturb (DND) lists and strict opt-in and opt-out rules that must be adhered to.

Regulations like the GDPR in Europe and the TCPA in the U.S. govern how businesses can collect, store, and use mobile numbers. Non-compliance can not only lead to blocked messages but also hefty fines.

For example, a U.S. company must have explicit consent from users before sending them marketing SMS and must provide an easy way to opt out of every message.

Understanding and addressing these factors will help businesses maintain high deliverability rates for their SMS campaigns, ensuring that messages reach their intended recipients efficiently and legally.

1. Keep a clean contact list

Invalid or outdated numbers can lead to high bounce rates and lower overall deliverability. 

Example:

An online fashion store sends a flash sale SMS to 50,000 contacts but notices a 20% bounce rate. After auditing their contact list, they found that many numbers were outdated or mistyped. They introduce an SMS verification step at checkout, reducing their bounce rate and ensuring messages reach real customers.

Regularly clean your contact list by:

• Removing inactive or invalid numbers
• Using opt-in methods to ensure recipients want to receive your messages
• Updating contact information periodically to avoid sending messages to non-existent numbers

2. Optimize message formatting & structure

Poorly formatted SMS messages can be blocked by carriers or ignored by recipients. To improve deliverability, keep messages short, avoid excessive special characters, and make the CTA clear.

Example:
Poor formatting:

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"🔥 BIG SALE!! Click NOW 👉 bit.ly/abcd to get 50% OFF!! Limited Time! 🚀"

Better formatting:

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"Hey [Name], our biggest sale of the season is live! Get 50% off sitewide. Shop now: www.brand.com"

By using a branded link instead of a generic shortener, the e-commerce brand avoids carrier spam filters and increases trust.

3. Timing and frequency

The timing and frequency of your messages can affect both user engagement and deliverability. 

Schedule SMS to arrive during optimal times based on customer behavior patterns and avoid sending too many messages in a short period, which can lead to unsubscribes or spam complaints.

Example:

An electronics store adjusts their cart abandonment SMS reminders from 30 minutes to 4 hours after customers leave the site. After analyzing the results, this timing adjustment significantly boosts recovery rates, as customers are more responsive later

4. Customer segmentation

Not all recipients should receive the same message. Segmenting your audience allows for personalized and relevant communication. Consider:

• Segment contacts by demographics, purchase history, or engagement
• Send targeted messages based on preferences and past interactions
• Use dynamic content for personalized, high-response messages

Generic messages don’t work for e-commerce brands. Segmenting customers ensures that messages are relevant, leading to higher open and conversion rates.

Example:
A skincare brand segments its customers into three groups:

• New buyers receive a welcome SMS with a 10% discount on their next purchase
• Frequent shoppers get exclusive early access to sales
• Inactive customers receive a “We miss you” message with a special offer

5. Ensure compliance with local & global SMS laws

Adhering to SMS regulations is non-negotiable for legal operations and maintaining customer trust.

Familiarize yourself with local and international laws such as GDPR in Europe or TCPA in the U.S. Always get consent before sending SMS, provide clear opt-out options, and maintain records of these consents.

6. Monitor & analyze delivery reports

Continuous monitoring and analysis of your SMS campaigns’ performance help in understanding delivery success rates and identifying areas for improvement.

Key metrics to monitor include:

• Delivery rates to detect potential carrier or formatting issues
• Failure reports to understand common reasons for non-delivery
• Response times to measure engagement and campaign effectiveness

Example:

An online pet supply store finds that messages to specific regions are blocked, leading to high undelivery rates. After analyzing reports and adjusting sender IDs with their SMS provider, they significantly improve deliverability in those areas.

By implementing these best practices, businesses can ensure their SMS messages reach the right customers, improve engagement, and drive more sales.

Choosing the right SMS provider can significantly impact SMS deliverability. Plivo CX, an omnichannel SMS management platform, offers robust SMS delivery strategies that ensure reliable, high-speed message delivery with advanced analytics and compliance support.