Dealing with SMS delivery failures can be quite stressful. In this helpful document, we'll delve into all the potential causes behind an SMS sending or delivery failure and offer step-by-step troubleshooting solutions to address them.
Typically, when an SMS fails to send or deliver, you can find the corresponding error message displayed in the conversation view. It will appear something like this:
When encountering errors in SMS sending or delivery process, the error message and error code will provide valuable insights on the issue and guidance on how to proceed. Here are some potential reasons for failure:
DND is enabled: If a contact has enabled Do Not Disturb (DND) on the SMS channel or overall, CRM will not send the SMS and an error will be displayed in the conversation screen.
Number is a landline number (Number validation): performs number validation to check if the contact's phone number is SMS-capable. If it is determined that the number is not SMS-capable, will skip sending the SMS and show an error in the conversations screen.
Sub-Account is new and undergoing ramped sending: For newly created sub-accounts, gradually increases sending limits to prevent spamming or phishing. Agencies can choose to remove these restrictions if desired.
Sub-Account has exhausted the daily quota set by the agency: Agencies can set a daily limit on SMS sending for each sub-account. When this limit is reached will skip sending SMS in bulk actions and automations. However, 1:1 SMS messages will still be sent to allow clients to reply to their leads. Agencies have control over these limits for each sub-account.
Sub-Account SMS sending privileges have been suspended: monitors error rates, opt-out rates, and carrier complaint rates for all sub-accounts to prevent spamming and phishing. If any of these thresholds are exceeded, SMS sending privileges for the sub-account will be suspended for a certain period. Any attempted SMS sending during this time will be skipped, and an error message will be displayed on the conversation screen. At the Twilio/LC Phone Layer:
Number is on Twilio's DND list: If the contact's number has previously opted out or received a carrier complaint, SMS messages will not be delivered unless the contact opts in by texting START to the Twilio number.
30001 - Queue overflow: Twilio queues messages based on the sending rate of the sender or account. Messages can only be queued for up to 4 hours before they automatically fail. The queue length limit can be reduced by setting a lower Validity Period within your Messaging Service settings or API requests.
30002 - Sub-Account suspended on the Twilio side: If your Twilio sub-account is suspended between the time of message send and delivery
At the Sender Carrier Network Layer:
30003 - Unreachable destination handset: The destination handset you are trying to reach may be switched off, unavailable, have insufficient signal, belong to a landline, or there might be an issue with the mobile carrier.
30004 - Message blocked: The destination number you are trying to reach may be blocked from receiving the message, have insufficient signal, belong to a landline, be on India's national Do Not Call registry, or there might be an issue with the mobile carrier. Additionally, if you send a message from a US/CA Toll-free number to an end user handset that has previously responded with "STOP" or another opt-out keyword, the message will be blocked.
Attachment file size exceeded
Geo permission issues for international SMS
The body exceeds the limit of 1600 characters: If you are using a trigger to send an SMS, check the body of the message and look out for any custom values, such as {{message.body}}. Messages will not send if the body exceeds the limit of 1600 characters. [Example: If someone replies via email and their email exceeds the character limit, the message will not send if there is a custom value of {{message.body}}]
