--- title: "SMS Delivery: Statuses, Troubleshooting, and Regional Guidelines" description: "All SMS notifications sent through your OnceHub account are recorded in your SMS logs. Use this article to help you understand delivery statuses, resolve com..." url: "https://help.staticso2.com/billing/sms-delivery-statuses-troubleshooting-and-regional-guidelines" --- All SMS notifications sent through your OnceHub account are recorded in your [**SMS logs**](https://help.staticso2.com/scheduleonce/insights-operations/billing-subscription-management/introduction-to-billing). Use this article to help you understand delivery statuses, resolve common delivery failures, identify sender information and ensure compliance with regional carrier requirements. *** Understanding SMS Delivery Status Definitions Your SMS logs display one of the following statuses for every message sent: * **Delivered:** The message has reached the recipient’s device. * **Sent:** The message was sent but a delivery receipt is pending. This is usually a temporary status while the message is in transit. * **Rejected:** The message was not sent because the phone number was identified as invalid. * ## **Failed:** The message was sent but could not be delivered to the recipient. [Section titled “Failed: The message was sent but could not be delivered to the recipient.”](#failed-the-message-was-sent-but-could-not-be-delivered-to-the-recipient) ## Troubleshooting Delivery Failures [Section titled “Troubleshooting Delivery Failures”](#troubleshooting-delivery-failures) When an SMS fails, OnceHub provides a specific error message to help you identify the cause. | **Error Message** | **Meaning** | **Recommended Resolution** | | ---------------------------------------- | ----------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **Illegal Number** | Invalid phone format. | Verify the recipient’s number and country code. | | **Absent Subscriber** | The number is disconnected/ inactive. | Confirm the mobile number with your customer. | | **Call Barred by User** | Recipient blocked incoming SMS. | Recipients must contact their carrier to unblock. | | **Portability Error** | The number recently moved between carriers. | Database sync issue; usually resolves within 24–48 hours. | | **Anti-Spam Rejection/ Invalid Message** | Carrier rejected the message because of the message content / sender ID | 1. Ensure the message doesn’t contain high-risk keywords (e.g., “loan”, “debt”). 2. See [**How to Manage Regional Limitations (Singapore & Turkey)**](https://help.staticso2.com/billing/sms-delivery-statuses-troubleshooting-and-regional-guidelines#how-to-manage-regional-limitations-singapore--turkey) section below for specific rules. | | **Handset Busy** | Device unable to receive (e.g., full inbox). | The system will automatically retry. If the error persists, manually try sending the message again later. | | **Network Error** | Carrier network congestion or outage. | This is usually a temporary carrier issue. Wait a few minutes and manually resend the message. | | **Unroutable** | Carrier cannot route to this number. | Check for regional limitations or verify the number. | | **Destination Unreachable** | General routing failure. | Verify the recipient’s number is correct. If it is, attempt to resend the message after a short delay. | | **Number Blocked by Carrier** | Carrier-level block on the device. | Recipients must contact their carrier to enable SMS. | | **Subscriber Opt-Out** | The user has unsubscribed. | See [**How Guests can Opt-Outs of SMS Notifications (US & Canada)** ](https://help.staticso2.com/billing/sms-delivery-statuses-troubleshooting-and-regional-guidelines#how-guests-can-opt-out-of-sms-notifications-us--canada)section below. | | **Prepaid - Insufficient funds** | Prepaid plans cannot accept SMS. | The receiver must top up their balance or check their mobile plan. | | **General Error** | Unknown carrier or internal error. | Wait for 15–30 minutes, then manually resend the notification from the SMS logs. If the error persists, [**Contact OnceHub Support**](https://support.oncehub.com/) for technical investigation. | *** ## How to Identify OnceHub Sender Information [Section titled “How to Identify OnceHub Sender Information”](#how-to-identify-oncehub-sender-information) OnceHub uses consistent Sender IDs to ensure high deliverability. You can share these Sender IDs with your customers so they can whitelist them or save them as a contact to prevent messages from being flagged as spam. * **United States:** 1-844-200-5585 * **Canada:** 1-204-272-8408 * **India:** Random Numeric Sender ID (e.g., 59039465) * **Rest of World:** Appear with the Sender ID **OnceHub** *** ## How to Manage Regional Limitations (Singapore & Turkey) [Section titled “How to Manage Regional Limitations (Singapore & Turkey)”](#how-to-manage-regional-limitations-singapore--turkey) Carrier policies in certain regions may impact delivery even when a **Sent** status is displayed. ### Singapore [Section titled “Singapore”](#singapore) SMS deliverability is highly restricted by local authorities. Automated messages are frequently blocked at the carrier level. **Recommendation:** Because OnceHub does not differentiate notifications by region, you cannot enable email alerts for specific countries. If you have customers based in Singapore, we recommend **enabling Email Notifications** in your **Booking Calendars** to ensure they receive meeting details. ### Turkey [Section titled “Turkey”](#turkey) Turkish carriers strictly filter messages containing URLs, often leading to immediate delivery failure. **Requirement:** Because OnceHub does not differentiate notifications by region, you cannot apply specific SMS templates to different countries. If you have customers based in Turkey, you must ensure your **SMS templates are plain-text only** and do not include links (e.g., Cancel or Reschedule links) to avoid carrier blocks. *** ## How Guests can Opt-Out of SMS Notifications (US & Canada) [Section titled “How Guests can Opt-Out of SMS Notifications (US & Canada)”](#how-guests-can-opt-out-of-sms-notifications-us--canada) In compliance with carrier regulations, recipients in the US and Canada can unsubscribe from all OnceHub notifications at any time using some standard Keywords. To opt-out, recipients can reply to any SMS with: **STOP**, **END**, **QUIT**, **CANCEL**, **UNSUBSCRIBE**, **REVOKE**, or **OPT OUT**. These keywords are **not case-sensitive**. Caution Opting out adds the recipient to a blocklist, preventing them from receiving any further SMS alerts from your OnceHub account.