Overview
Outbox AI supports three carriers: Twilio, Vonage, and Telnyx. Each shines in different markets and price brackets. This guide will help you pick the right one for every client.Choosing a Provider
Compare the three carriers to find the best fit for your use case.
Twilio
Twilio
Best for: United States (and Canada)
Strengths
- ✅ Quick, self-serve setup—buy numbers in minutes
- ✅ High concurrency limits—perfect for large campaigns
- ✅ Built-in voicemail detection (saves wasted agent talk-time)
- ✅ Verified Caller ID lets you mask calls with a client’s existing phone number
- ✅ Direct GoHighLevel SMS integration—same number for calls and texts
Weak Points
- ❌ Charges by the minute (rounded up), so a 9-second voicemail costs a full minute
- ❌ Non-US pricing is steep—about 7¢ USD per minute in Australia
Vonage
Vonage
Best for: Non-US regions where per-second billing matters
Strengths
- ✅ Bills per second—a 30-second call costs half a minute
- ✅ Slightly cheaper headline rates than Twilio outside the US
Weak Points
- ❌ No native voicemail detection (Outbox uses its own transcript-based fallback)
- ❌ No verified caller IDs
- ❌ On-boarding is manual: email a rep, fill in forms, wait for approval
- ❌ No GoHighLevel SMS tie-in, so you’ll juggle separate SMS and voice numbers
When to use: Mid-size international campaigns where per-second pricing outweighs the admin hassle.
Telnyx
Telnyx
Best for: International markets (AU, UK, NZ, Europe) when cost is king and you still want Caller ID maskingWorks great in: AU, UK, NZ, and most European countries
Strengths
- ✅ Significantly cheaper than Twilio in most international markets (40-60% savings)
- ✅ Supports verified caller IDs—pair it with a Twilio SMS number for a “one-number” experience
- ✅ Modern dashboard, good documentation
- ✅ Competitive rates in AU, UK, NZ, and European countries
Weak Points
- ❌ Charges by the minute (no per-second savings)
- ❌ Occasional reliability quirks: sudden number blocks, quirky concurrency caps
- ❌ No built-in voicemail detection
- ❌ No direct GoHighLevel SMS integration (hence the Twilio-plus-Telnyx combo)
Practical Hybrid Stack
1
Twilio for SMS + Inbound
Buy a Twilio number → connect to GoHighLevel for SMS + inbound voice
2
Telnyx for Outbound
Buy a Telnyx number → set Twilio number as a verified caller ID
3
Save on Costs
Make outbound calls via Telnyx and save 40-60% on international rates
Twilio Setup
Twilio is the gold standard for US/Canada traffic. Follow these steps to set up a number and connect it to Outbox AI.1. Create (or Open) a Sub-Account
1
Log In
Visit console.twilio.com
2
Navigate to Sub-Accounts
Click your workspace name → Sub-Accounts → Create new sub-account
3
Name Your Sub-Account
Name it after your client to keep billing and logs separate
2. Build the Regulatory “Bundle” (If Required)
Many countries require proof-of-business before you can purchase phone numbers. Twilio calls this a “regulatory bundle.”
US/Canada toll-free and local numbers typically don’t require bundles.
Mobile numbers in most countries (including AU, UK, NZ) do require
compliance documentation.
1
Navigate to Regulatory Compliance
In the left menu choose Phone Numbers → Regulatory Compliance
2
Create Bundle
Click Create Bundle and fill in: - Country: Select your target
country - Number Type: Mobile, Local, or Toll-Free - Business Type:
Independent software vendor (or appropriate category)
3
Upload Documents
Twilio typically asks for: - Business name - Business address -
Business registration number (ABN for AU, EIN for US, Companies House
for UK, NZBN for NZ) Accepted documents: - Utility bills - Lease
agreements - Business registration certificates - Tax documents Each file
must show at least two of the required data points; upload multiple files if
needed. Registry Links: - ASIC
(Australia) - Companies House
(UK) - New
Zealand Companies Office
4
Submit and Wait
Submit; approval usually takes 24-48 hours depending on the country
3. Buy a Phone Number
1
Navigate to Buy a Number
After the bundle is approved (or immediately for US/Canada), go to Phone
Numbers → Buy a number
2
Filter by Country and Capabilities
Filter for your target country and Capabilities = Voice & SMS
3
Choose Your Number
Select a number that matches your needs: - Mobile (AU: 614, UK: 447, NZ:
642) - Best for SMS + voice - Local (US/Canada area codes) - Geographic
presence - Toll-free (US: 800/888, AU: 1800, UK: 0800) - Free for
callers
4
Buy
Click Buy to purchase the number
| Region | Outbound | Inbound |
|---|---|---|
| US/Canada | ~1¢ USD | ~0.5¢ USD |
| UK | ~3¢ USD | ~1¢ USD |
| Australia | ~7¢ USD | ~1¢ USD |
| New Zealand | ~6¢ USD | ~1¢ USD |
4. A2P Registration (US SMS Only)
If you’re sending SMS messages to US numbers, you must register for A2P (Application-to-Person) messaging. This is a US regulation to reduce spam.
What is A2P?
A2P (Application-to-Person) registration is required by US carriers for business SMS messaging. It verifies that you’re a legitimate business sending approved content. Two Options:Standard Registration (Recommended)
Standard Registration (Recommended)
Timeline: 4-6 weeks
Cost: ~$15-50 one-time fee
Throughput: Up to 4,500 messages per minuteRequirements:
Cost: ~$15-50 one-time fee
Throughput: Up to 4,500 messages per minuteRequirements:
- Business EIN (Employer Identification Number)
- Business website
- Business address
- Description of your SMS use case
- Sample message templates
1
Navigate to A2P Registration
Twilio Console → Messaging → Regulatory Compliance → A2P 10DLC
2
Register Your Business
Submit your business information and EIN
3
Create Brand
Describe your brand and how you’ll use SMS
4
Create Campaign
Define your use case (appointment reminders, customer service, marketing, etc.)Submit sample message templates
5
Wait for Approval
Approval typically takes 4-6 weeks. You’ll receive email updates on progress
6
Assign Numbers
Once approved, assign your US numbers to the campaign
Low Volume (Quick Start)
Low Volume (Quick Start)
Timeline: Instant
Cost: Free
Throughput: Only 5-10 messages per minuteIf you’re just testing or sending very low volumes, you can skip full A2P registration. However, your messages will be heavily throttled.
Cost: Free
Throughput: Only 5-10 messages per minuteIf you’re just testing or sending very low volumes, you can skip full A2P registration. However, your messages will be heavily throttled.
Non-US Numbers
If you’re not sending SMS to US numbers (e.g., AU → AU, UK → UK), you can skip A2P registration entirely. It’s only required for US SMS traffic.International SMS: Other countries have their own regulations, but most
don’t require pre-registration like the US does. Always check local
requirements for your target market.
5. Copy Credentials into Outbox AI
1
Get Your Credentials
Back in the Twilio console dashboard, copy Account SID and Auth
Token
2
Add to Outbox AI
In Outbox AI, open Telephony → Twilio and paste both values
3
Select Your Number
The number you just bought appears in the list—select it for outbound voice
and SMS
6. (Optional) Add a Verified Caller ID for Masking
If your client wants calls to display their existing business line:1
Navigate to Verified Caller IDs
Twilio left menu → Verified Caller IDs → Add new
2
Enter Business Number
Enter the business number; Twilio sends an SMS or voice code for
verification
3
Verify
Once verified, you can choose that caller ID when launching campaigns
Important: Verified IDs work for outbound only; inbound calls still
land on the Twilio number.
Vonage Setup
Vonage bills by the second and can be cheaper than Twilio outside the US, but the onboarding is more manual. Follow these steps to secure a number and connect it to Outbox AI.1. Log In and Fund the Account
1
Visit Dashboard
Visit dashboard.nexmo.com (same portal,
simply re-branded as Vonage)
2
Add Balance
Add a small balance—Vonage won’t let you request numbers on a £0 wallet
2. Request a Phone Number
1
Navigate to Buy Numbers
In the left sidebar, click Phone Numbers → Buy Numbers
2
Search for Number
Choose the target country and search
3
Request (Not Buy)
Click Request; instead of instant purchase, the portal creates a ticket
4
Provide Documents
A Vonage rep emails you for supporting documents—usually: - Proof of
business name and address (utility bill, lease, ASIC extract, etc.) -
Business registration ID (ABN, Companies House number, EIN, etc.)
5
Wait for Approval
Email the files back; approval typically lands within 24–48 hours The number
appears in your dashboard under My Numbers once approved and billed
3. Grab Your API Credentials
1
Navigate to API Settings
From the top menu, choose Settings → API Settings
2
Copy Credentials
Copy the API Key and API Secret
4. Connect Vonage to Outbox AI
1
Open Integrations
In Outbox AI, open Settings → Company → Integrations
2
Select Vonage
Select Vonage
3
Paste Credentials
Paste the API Key and Secret; click Save
4
Assign Numbers
Your purchased numbers populate in the list—assign as needed to voice agents
Telnyx Setup
Telnyx often offers lower per-minute rates than Twilio in many international markets (especially AU, UK, and Europe), but it lacks GoHighLevel SMS integration and native voicemail detection.Recommended Strategy
Use Twilio for inbound and SMS (so everything lands in GoHighLevel) Use
Telnyx for outbound voice, masking the calls with the same Twilio number
through “verified caller ID” This gives you the best of both worlds: Twilio’s
reliability + Telnyx’s pricing.
Popular in: Australia, UK, New Zealand, and European markets where Telnyx
rates are significantly lower than Twilio.
Step 1 – Secure a Twilio SMS / Inbound Line
1
Buy Twilio Number
Purchase a Twilio number in your target country, plug the SID & Auth
Token into Outbox AI, and connect it to GoHighLevel
2
Assign to your agent
Keep this number for inbound calls and all texting
3
Add to GoHighLevel (Optional)
Add this number into your GoHighLevel account if you want SMS Capabilities
Step 2 – Buy a Telnyx Outbound Line
1
Search and Buy
In Telnyx, choose Numbers → Buy Numbers and purchase a voice-capable
number in your target country
2
Complete Compliance
Complete the compliance prompts (business documents, address, registration
number, etc.)
Step 3 – Create a SIP Trunk
1
Navigate to SIP Trunks
Voice → SIP Trunks → Create SIP Connection
2
Trunk Details
Name it, choose FQDN mode, click Create
3
Authentication & Routing
Leave FQDN empty and scroll down to Outbound Calls Authentication -
Set a unique Username (e.g.,
outbox_user) - Set a strong Password- Click Next
4
Configuration
Leave this screen as the defaults and click Next
5
Inbound
Leave this screen as the defaults and click Next
6
Outbound Settings
Configure your outbound call settings: - Localization Country – Select
the country you’ll be calling (e.g., Australia, US, UK) - Caller ID
Override – Paste the Twilio number you purchased in Step 1 This makes
outbound calls display your Twilio number instead of the raw Telnyx number.
7
Configure Voice Profile
Create or select a Voice Profile and whitelist the destinations you plan
to dial
8
Assign Number
Assign the Telnyx number to this SIP trunk
Step 4 – Add Telnyx Number to Outbox AI
Now connect the Telnyx SIP trunk to Outbox AI.1
Navigate to Phone Numbers
In Outbox AI, go to Company Settings → Phone Number tab
2
Add SIP Number
Click Add SIP Number
3
Configure SIP Details
Fill in the connection details: - Name – Label for this number (e.g.,
“Client Name - Telnyx Outbound”) - Phone Number – The Telnyx number you
purchased (e.g.,
+61412345678) - SIP Domain – sip.telnyx.com (or
192.76.120.10 if that doesn’t work) - SIP Username – The username you
set in Step 3 - SIP Password – The password you set in Step 34
Configure Billing
Set your billing preferences: - Rebilling – Toggle ON if you want to
charge clients for usage, OFF if you’re covering costs - Outbound Cost –
Set to
0.033 (3.3¢ per minute for AU, adjust for other countries) -
Billing Type – Keep Bill per minute ON (Telnyx charges by the
minute)5
Save
Click Save to add the number to your account
Result
✅ All outbound calls travel via Telnyx (typically 40-60% cheaper than Twilio in most markets)✅ The callee’s phone displays the familiar Twilio number
✅ Inbound calls and SMS still hit GoHighLevel through Twilio Estimated Savings:
- Australia: ~3.3¢/min vs ~7¢/min (save ~50%)
- UK: ~2¢/min vs ~3¢/min (save ~33%)
- Europe: ~2-3¢/min vs ~4-5¢/min (save ~40%)
Cost-Control Reminders
Per-Minute Billing
Per-Minute Billing
Telnyx charges by the minute (unlike Vonage’s per-second billing). A 61-second call costs 2 minutes.
Test Concurrency
Test Concurrency
Telnyx occasionally rate-limits new numbers. If calls start failing, raise a
support ticket to increase limits.
Watch for Blocks
Watch for Blocks
Keep an eye on “number blocked” errors mid-campaign. Swap a fresh Telnyx
number if needed.
Document Your Stack
Document Your Stack
With a multi-provider setup (Twilio + Telnyx), document which number does what so your team doesn’t get confused.
Best Practices
Start with One Provider
Start with One Provider
Don’t try to set up all three at once. Pick the best fit for your primary market and master it first.
- US/Canada clients? Twilio
- International clients (per-second billing)? Vonage
- Cost-conscious international (AU/UK/NZ/Europe)? Telnyx + Twilio combo
Use Sub-Accounts for Client Separation
Use Sub-Accounts for Client Separation
Create separate sub-accounts (Twilio) or labeled numbers (Vonage/Telnyx) for
each client. This makes billing tracking and troubleshooting 10x easier.
Test Before Going Live
Test Before Going Live
Always send test calls before launching campaigns: 1. Test inbound and
outbound 2. Verify caller ID displays correctly 3. Check SMS delivery (if
applicable) 4. Confirm call quality and latency
Monitor Your Balance
Monitor Your Balance
Set up billing alerts in your provider dashboard. Running out of credits
mid-campaign is embarrassing and costly.
Document Your Verified Caller IDs
Document Your Verified Caller IDs
Keep a spreadsheet of which client uses which caller ID, especially if you’re managing multiple masked setups.
Troubleshooting
Numbers Not Appearing in Outbox AI
Numbers Not Appearing in Outbox AI
Problem: You’ve bought a number but it’s not showing up.Solutions:
- Double-check credentials (SID, Auth Token, API Key) are correct
- Refresh the Outbox AI page
- For Twilio, ensure you’re using the correct sub-account credentials
- For Telnyx SIP, verify the SIP domain is correct (
sip.telnyx.comor192.76.120.10)
Calls Failing to Connect
Calls Failing to Connect
Problem: Outbound calls aren’t connecting. Solutions: - Check
balance: Ensure your provider account has sufficient funds - Verify number
status: Some numbers need activation or compliance approval - Test with a
different number: Rule out number-specific issues - Check concurrency
limits: You may have hit your max simultaneous calls - Review error
logs: Outbox AI shows detailed error messages in Call Logs
Caller ID Not Displaying Correctly
Caller ID Not Displaying Correctly
Problem: The wrong number is showing on outbound calls. Solutions: -
Twilio: Verify the caller ID is properly verified in Verified Caller IDs -
Telnyx: Check the Caller ID Override is set correctly in the SIP trunk -
Both: Ensure you’ve selected the correct caller ID in Outbox AI when
setting up the campaign
SMS Not Working
SMS Not Working
Problem: Text messages aren’t sending or receiving. Solutions: -
Twilio only: SMS doesn’t work with Vonage or Telnyx in GoHighLevel -
Verify the Twilio number has SMS capability enabled - Check that the number is
properly connected to GoHighLevel - Ensure you have A2P 10DLC registration if
sending to US numbers
High Latency or Poor Call Quality
High Latency or Poor Call Quality
Problem: Calls have delays or sound choppy. Solutions: - Check your
internet connection: Voice requires stable bandwidth - Test from a
different location: Rule out local network issues - Try a different SIP
region: For Telnyx, switch to a closer POP - Contact provider support:
There may be routing issues on their end
Regulatory Bundle Rejected
Regulatory Bundle Rejected
Problem: Twilio rejected your compliance documents.Solutions:
- Ensure documents show at least 2 of 3 required data points (name, address, registration number)
- Use recent documents (under 3 months old)
- Make sure text is legible (no blurry photos)
- Upload multiple documents if one doesn’t cover all requirements
- Check the rejection email for specific issues
A2P Registration Stuck or Rejected
A2P Registration Stuck or Rejected
Problem: Your A2P 10DLC registration is taking too long or was rejected.Solutions:If Stuck (over 6 weeks):
- Contact Twilio support with your campaign ID
- Check for any pending actions in the A2P dashboard
- Verify your business EIN is valid and matches official records
- Review the rejection reason carefully
- Common issues:
- Sample messages look like spam or scams
- Business website doesn’t match your description
- Use case is unclear or too broad
- EIN doesn’t match business name
- Revise your campaign description to be more specific
- Provide clearer sample message templates
- Resubmit with corrections
US SMS Still Throttled After A2P
US SMS Still Throttled After A2P
Problem: SMS messages are still slow even after A2P approval.Solutions:
- Verify your phone number is actually assigned to the approved campaign
- Check campaign status—it may show “approved” but still be processing
- Allow 24-48 hours after approval for full throughput to activate
- Review your campaign’s assigned throughput tier (some use cases get lower limits)
- Contact Twilio if throttling persists beyond 48 hours