### Answer --- When outbound calls fail with Retell-owned numbers, check the call history for the

disconnection_reason

and SIP error code in the detailed log—this usually identifies the root cause. [(1) ]() Possible disconnection reasons for failed outbound calls include: -

invalid_destination

– destination phone number is invalid -

telephony_provider_permission_denied

– SIP trunk authentication failed -

telephony_provider_unavailable

– telephony provider is not available or has errors -

marked_as_spam

– call is marked as spam -

dial_failed

– SIP error codes not available or error unknown If using numbers purchased from Retell: - Make sure the destination number can accept the call—currently, numbers purchased from Retell can only make calls to US numbers. If your number is marked as spam: - Purchase a new number and warm it up before pouring all traffic to it (slowly add outbound traffic) - Increase the pickup rate - Register the number with the spam remediation feature (verified phone number) Since your SIP trunk works instantly but Retell-owned numbers fail, this could indicate a spam/carrier block or a provider-side issue with Retell's telephony. I'd recommend checking the call detailed log for the specific

disconnection_reason

and SIP error code, and if the logs don't clarify the issue, reaching out to Retell support directly. Check out these potentially useful sources: - [Debug outbound connection issues]() - [Platform Changelogs | Retell AI]() - [Twilio SIP Trunking Setup]()

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

​ To learn more, see the sources I considered: [[1] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) ​

@AI Evy Batch calls consistently fail when using Retell-owned US/CA numbers. Batches get stuck on Send or throw network errors. Same CSV and workflow works instantly via SIP trunk. This appears to be an issue with Retell Telephony batch dispatcher or number allocation.

### Answer --- Based on the symptoms you're describing (batches stuck on "Send" or network errors with Retell-owned numbers while SIP trunk works fine) , here's what to check: 1. Check Call History Logs Review the call history and detailed log for each failed call—it contains the

disconnection_reason

, SIP error code, and error message which should identify the root cause. [(1) ]() 2. Relevant Disconnection Reasons For calls that show status

not_connected

, look for these reasons: -

telephony_provider_unavailable

– telephony provider is not available or has errors -

telephony_provider_permission_denied

– SIP trunk authentication failed -

marked_as_spam

– call is marked as spam by carriers -

dial_failed

– SIP error codes not available or error unknown 3. Spam/Carrier Blocking If your Retell-owned numbers are experiencing high outbound volume without warmup or have low pickup rates, they may be marked as spam by carriers. To remedy this: - Purchase a new number and warm it up before pouring all traffic to it (slowly add outbound traffic) - Increase the pickup rate - Register the number with the spam remediation feature (verified phone number) 4. Retell Number Limitation Numbers purchased from Retell can currently only make calls to US numbers. Since your SIP trunk workflow works instantly with the same CSV, this strongly suggests the issue is specific to Retell's telephony infrastructure or the specific numbers allocated. The "stuck on Send" behavior isn't documented as a standard disconnection reason, which may indicate a platform-side issue. Recommended Next Step: Check the detailed logs for any available error codes. If logs show no clear reason or the issue persists, this warrants direct contact with Retell support as it may be a dispatcher or number allocation

issue on their end. - [Contact Sales]() - [Retell AI GitHub]() Would you like a general answer based on my knowledge instead?

​ To learn more, see the sources I considered: [[1] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.