### Answer Based on the available documentation, I don't have specific information about the exact geographic location of Retell's servers. What I can share is the IP block information for Retell's SIP server traffic: [(1) ]() - **IP block for all regions**:

18.98.16.120/30

- **United States only**:

143.223.88.0/21

and

161.115.160.0/19

- **Retell SIP server URI**:

sip:sip.retellai.com

The documentation notes that "Some non US traffic might go from IPs not listed above, but will be migrated to the first IP block by 12/03/2025." Since the US-only IP blocks are explicitly labeled as such, and there's a general "all regions" block, it suggests Retell handles traffic from multiple regions. However, the specific server locations (e.g., whether there's a European presence) aren't documented in the sources I have access to. **My suggestion**: Reach out to Retell support directly to confirm server locations for UK/European traffic before making your Twilio region decision. This will ensure you get the most accurate guidance for minimising latency. Check out these potentially useful sources: - [Custom Telephony Overview]() - [AI in SIP Calling & Telephony Solutions]() Would you like me to try to provide a general answer based on my knowledge instead?

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] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) ​

### Answer Based on my general knowledge, here's what I can share about server location considerations for voice AI platforms: General guidance for UK-based deployments: Most cloud-based voice AI platforms use distributed infrastructure, often leveraging providers like AWS, GCP, or similar. For UK/European users, latency is typically influenced by: 1. Where your telephony provider routes calls - Twilio offers localized termination URIs near your region [(1) ]() 2. The voice AI platform's processing servers 3. Your end users' locations For Twilio specifically: The documentation recommends using a localized termination URI near your region for better performance. You can find localized URIs in the Twilio console. Practical recommendation: Since the documentation doesn't specify exact Retell server locations, choosing the Twilio region closest to your callers (Ireland for UK) is a reasonable approach. The latency between major cloud regions (e.g., Ireland to US East) is typically 70-100ms, which is manageable for voice applications. For the most accurate guidance on Retell's infrastructure and optimal configuration for UK deployments, I'd recommend reaching out to Retell support directly—they can confirm whether there's European server presence that would affect your Twilio region choice.

​ To learn more, see the sources I considered: [[1] Twilio](https://docs.retellai.com/deploy/twilio) ​

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