3CX v16 Alpha – Telnyx Inbound SMS not working


Recently 3CX released the Update 7 Alpha version with SMS support.

Having clients that were looking forward for the option to centralize SMS messages to call queues or agents, we created a new instance and started the setup with Telnyx. They will give you $10 on credit for registering, ideal to do some tests.

Once the setup for Telnyx was finished, we could send out SMS but not receive any type of messages.

For this instance, we use a custom FQDN with certificates.

The error we received on our 3CX when trying to test the service was “UNABLE_TO_VERIFY_LEAF_SIGNATURE”

All ports needed were open and we could run a firewall test with no issues.


It turned out that we were missing intermediate certificates on our Nginx and that was causing the problem.

Check your PEM file here:


If it’s just the certificate, you will need to add the chain with the intermediate CA.

You can generate the entire chain by using your PEM on this site:


Or amend it manually using the CA/bundle for your certificate.

Once the certificate has the entire chain, reboot your server and your inbound SMS should start working again.

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