SMS Delivery and Limitations

When sending SMS Campaigns in Jomablue, most messages are delivered successfully within seconds. However, some recipients, particularly those with international numbers, may not receive your message.

This happens because SMS delivery is a “best-effort” system: Jomablue ensures messages are handed off correctly to trusted gateways, but final delivery depends on carrier systems, international routing, message type, and local regulations.

Understanding how SMS delivery works can help you set realistic expectations and improve campaign effectiveness.

Why Delivery Isn’t Guaranteed

Once your message leaves Jomablue, several factors can affect whether it reaches the recipient:

Network & Carrier Factors

• Delivery receipts (DLRs) confirm handoff to the carrier, not the device: Some SMS gateways confirm that the message reached the carrier, but they cannot confirm delivery to the recipient’s handset
  
• Network congestion or outages: Carriers may delay or drop messages under heavy load
  
• Carrier filtering: Bulk, promotional, or unregistered messages may be automatically blocked
  

Regulatory & Country Factors

• Regulatory restrictions: Some countries (e.g., Malaysia, India, Singapore, China) require carriers to block certain international messages
  
• Sender ID limitations: In some regions, the displayed sender may be replaced or removed
  

Message & Number Factors

• Incorrect or unsupported numbers: Missing country codes, wrong formats, or inactive numbers can prevent delivery
  
• Message type, encoding, and length: Promotional vs transactional messages, Unicode characters (like emojis), or long messages may be split or rejected
  

Note: These limitations are not caused by Jomablue; they reflect the constraints of SMS technology and local regulations.

How SMS Delivery Works

Once an SMS is sent from Jomablue, it passes through several stages before reaching the recipient:

Jomablue → SMS Gateway → International/Local SMS Aggregators → Recipient Carrier → Recipient Device

• Jomablue: Your message is created and handed off to the SMS gateway
  
• SMS Gateway: A trusted provider forwards the message toward the recipient’s carrier network
  
• International/Local SMS Aggregators: Messages crossing borders may route through intermediary networks to reach the destination carrier
  
• Recipient Carrier & Device: The carrier attempts delivery to the recipient’s phone
  

Note: Jomablue can track whether the message reaches the gateway, but cannot guarantee delivery to the recipient’s device.

International & Regional Considerations

SMS delivery rules vary by country:

• Regulatory filtering: Some countries block or limit international messages
  
• Carrier spam filtering: Carriers may block messages based on volume, sender ID, or message type
  
• Sender ID limitations: The sender’s displayed name may be replaced or removed in certain regions
  

Tip: Testing small batches in the target country helps identify local delivery restrictions before a full campaign.

Best Practices to Improve SMS Success

Follow these steps to maximise delivery and engagement:

• Validate numbers: Use E.164 format (e.g., +60123456789) and remove leading zeros after the country code
  
• Test campaigns regionally: Send small batches to confirm international routing works as expected
  
• Collect valid opt-ins: Ensure attendees consent to receive messages and follow carrier-specific rules
  
• Use transactional messaging when possible: Transactional messages often have higher delivery priority than promotional messages
  
• Check message length and encoding: Avoid unsupported characters or excessive length that may split or be rejected
  
• Leverage alternative channels: For critical communications, use email or app push notifications alongside SMS