Check the message status
1
Open the conversation
Navigate to Conversations and find the contact whose message was not delivered. Open their conversation thread.
2
Look for delivery indicators
Check the status icon next to the sent message:
- Sent — The message was sent to the carrier but delivery is not confirmed
- Delivered — The carrier confirmed delivery to the recipient’s device
- Failed — The message could not be delivered; check the error details
- Undelivered — The carrier accepted the message but could not deliver it
3
Review the error code
Click on the failed message to view the error code and description. Common error codes are listed in the table below.
Common error codes
A2P 10DLC registration
If your messages are consistently being blocked or filtered:1
Verify your brand registration
Go to Settings > Phone Numbers and check your A2P 10DLC registration status. Ensure your brand is registered and approved.
2
Check your campaign registration
Each use case (marketing, notifications, etc.) requires a separate campaign registration. Verify that the campaign matching your message type is active.
3
Wait for approval
New registrations can take 1-4 weeks for approval. Messages sent before approval may be filtered. Avoid sending high volumes during this period.
Message content issues
Carriers actively filter messages that look like spam. Avoid these common content triggers:- ALL CAPS text — Carriers flag messages with excessive capitalization
- Shortened URLs (bit.ly, tinyurl.com) — Use full branded URLs instead
- Promotional language without opt-out instructions — Always include “Reply STOP to unsubscribe”
- Excessive special characters or emojis — Keep messages professional and clean
- Identical messages sent in bulk — Vary your message content to avoid pattern detection
Recipient issues
Contact has opted out
If a contact replied STOP to a previous message, they are automatically added to the opt-out list. You cannot send them SMS until they opt back in by replying START. To check opt-out status:- Open the contact record
- Look for the DND (Do Not Disturb) settings
- Check if SMS is marked as opted out
You must not manually remove a contact from the opt-out list without their explicit consent. Doing so violates carrier regulations and can result in your number being blocked.
Invalid phone number
- Verify the phone number format includes the country code (e.g., +1 for US)
- Remove any extra spaces, dashes, or parentheses
- Confirm the number is a mobile number, not a landline
Sending limits and throttling
The HoopAI platform enforces sending limits based on your phone number type and registration status:
If you are hitting sending limits, messages may be queued and delivered with delays, or they may fail entirely.
Troubleshooting steps summary
1
Check message status and error codes
Review the conversation thread for failed message indicators and error codes.
2
Verify A2P registration
Ensure your brand and campaign are registered and approved for 10DLC.
3
Review message content
Remove spam triggers such as shortened URLs, all caps, and missing opt-out language.
4
Confirm recipient eligibility
Verify the contact has not opted out and the phone number is valid and mobile.
5
Check sending limits
Ensure you are not exceeding the rate limits for your number type.
FAQs
Why are my messages marked as sent but not delivered?
Why are my messages marked as sent but not delivered?
A status of Sent means the message was accepted by the carrier network but delivery to the handset has not been confirmed. This can happen if the recipient’s phone is off, out of range, or if the carrier is experiencing delays. Wait and check again later.
Can I send SMS to landlines?
Can I send SMS to landlines?
No. Landlines cannot receive SMS messages. If you attempt to send to a landline, the message will fail with error code 30006. Verify that your contact list contains mobile numbers only.
How long does A2P 10DLC registration take?
How long does A2P 10DLC registration take?
Brand registration is typically approved within a few business days. Campaign registration can take 1-4 weeks depending on the use case and carrier review process.
My toll-free number messages are being filtered. What should I do?
My toll-free number messages are being filtered. What should I do?
Submit your toll-free number for verification under Settings > Phone Numbers. Unverified toll-free numbers have strict rate limits and are more likely to be filtered by carriers.