What causes failed delivery of SMS or IVR calls and how to fix it?

Premium quality routes are used by engageSPARK to send IVR calls and SMS text messages in over 200 countries. Behind the complex system, there are many variables that may affect the delivery of your messages—from telco bottleneck to server connectivity issues, and other issues affecting any service component. It cannot be guaranteed at all times that every SMS or IVR call will be delivered at the exact time you scheduled it to go out. To prevent any negative service impact due to telco or server issues, we do high-level system monitoring to detect any disruptions and promptly implement corrective actions.

Unexpected problems may arise, especially in developing countries where network signal is weak in certain geographical areas and thus often have issues with dropped calls, keypress capture, delayed delivery and sometimes failed delivery. With the strong partnerships we have with telcos worldwide, we manage to report these issues and get things fixed. We provide our best effort in getting the voice calls and SMS out as quickly and as close to the requested time as possible.

Checklist to ensure proper message delivery

Engagement and/or account settings

  1. Check the Start time in Step 3 to make sure it is scheduled properly and check the engagement status (scheduled, running, stopped, completed) to determine the delivery lead time.
  2. Make sure you have sufficient funds to cover the cost of sending messages.
  3. Review our Anti-Spam Policy and be sure your messages does not fall under prohibited content or spam. If you did not violate our terms and anti-spam policy, please contact support so we can review and whitelist your account. Our spam filter may flag accounts that send 7 or more messages using only the test credits.
  4. Use only numeric Caller ID for Voice or registered alpha Sender ID for SMS in Step 3.
  5. Validate the recipient’s phone number. Check whether the entry is in international format: Country Code +  Local Area Code + Local Phone Number
  6. Limit the SMS to 3 multi-part SMS or about 420 characters to ensure delivery of the entire message. This limitation may vary depending on the telco and/or destination country and the user’s handset.
  7. If you have multiple two-way SMS engagements that are ongoing (in “running” status), make sure to add a Keyword Prefix—so the system can differentiate which incoming SMS text messages are associated with which engagement.

Android relay app settings

Are you using the Android Relay App to send/receive voice calls or text messages? If yes, make sure:
✓ Android phone must be with good phone signal.
✓ Internet connection or WiFi is always available—Android phone not in airplane/flight mode.
✓ Airtime credits are sufficient to send the messages.
✓ Relay App must be activated (circle tap button in green).

Recipient’s phone or end-user network issues

In most cases, we found no delays in forwarding the messages from our server to the end user’s telco network. The messages may not be delivered on time, which can be due to the following issues:

  • User has weak phone signal
  • Network disruption during the time the message was sent
  • Problem with user’s mobile handset or SIM
  • Recipient’s phone settings: airplane/flight mode is activated; inbox memory is full; call barring is turned on.

Check message delivery status from the detailed report

To know how many SMS text messages or voice calls were delivered or have failed, check the Statistics on Reports Summary page. For Voice engagements, click Download detailed report to get data on why the call was not answered (see “No Answer Reason column). The spreadsheet report will show if the system detected network issues e.g. network congestion, no phone signal or if the call was canceled by the contact. More on Reports »


Have questions or need a little extra help?