Why Is My Deleted SIP Domain Name Still Unavailable? Understanding SIP Domain Cooldown in Twilio – Twilio Support

Issue

When working with Twilio SIP Domains, you may encounter a situation where you delete a SIP Domain (or even the entire subaccount that owned it), but the domain name remains unavailable for reuse. This article explains why this happens, what to expect, and your options for moving forward.

Product

Elastic SIP Trunking

Environment

Twilio Console

Cause

SIP Domain Names Must Be Globally Unique

Every SIP Domain name (e.g., yourdomain.sip.twilio.com) must be unique across all Twilio accounts and subaccounts. This ensures that calls are routed correctly and securely.

Cooldown (Quarantine) Period After Deletion

When you delete a SIP Domain, Twilio places the domain name in a "cooldown" or "quarantine" state. This period typically lasts up to 30 days. During this time, the domain name cannot be reused—even if you delete the subaccount that owned it or create a new subaccount.

Why Is There a Cooldown?

The cooldown period helps prevent routing issues and potential security risks that could arise if a domain name were immediately reused by another account or subaccount.

Common Scenarios

Deleted SIP Domain, Created New Subaccount, Name Still Unavailable:
Even if you delete the subaccount and create a new one, the previously used SIP Domain name will remain unavailable until the cooldown period expires.
Testing Workflows and Automation:
If your workflow involves creating and deleting subaccounts and SIP Domains for testing, you may run into this limitation. The cooldown applies regardless of how the subaccount was deleted.

Resolution

Wait for the Cooldown to Expire: The SIP Domain name will become available again after the cooldown period (usually up to 30 days from deletion).
Choose a Different SIP Domain Name: For immediate needs, select a new, unique SIP Domain name.
Business-Critical Need for Immediate Reuse: If you have a critical need to reuse the exact SIP Domain name before the cooldown expires, reach out to Twilio Support to discuss your use case. In most cases, the cooldown cannot be bypassed due to platform design and security requirements.

Frequently Asked Questions

Can I set a flag or request an override to bypass the cooldown?

No. The cooldown is a fundamental part of Twilio’s architecture to ensure security and data integrity. There is no account flag or override to change this behavior.

Does deleting the parent account or subaccount release the SIP Domain name?

No. The SIP Domain name remains in cooldown even if the subaccount is deleted.

How can I avoid this in my testing workflows?

Consider using unique SIP Domain names for each test run, or plan for the cooldown period in your automation.

Additional Information

SIP Domain names are globally unique and subject to a cooldown period after deletion.
The cooldown typically lasts up to 30 days and cannot be bypassed.
For immediate needs, use a different SIP Domain name.
If you have a business-critical need, contact Twilio Support to discuss your options.

For more information on SIP Domains, see Twilio SIP Domain documentation .

If you have further questions, our support team is here to help.