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Easybell treats username/password registration, Trusted IP, and Trusted FQDN as different connection modes. For inbound FQDN delivery, point Easybell to the platform SIP FQDN, then authenticate the incoming traffic on the platform by source address.

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Choose the Easybell path

Make sure the FQDN connection is enabled for the Easybell product. Configure the platform SIP FQDN as the trusted destination without a sip: prefix, send the DID in +E.164, and use the source list that matches the selected transport.
The FQDN feature on a plain SIP trunk isn’t self-service — request it by emailing support@easybell.de. It costs roughly €10/month and can take several days to activate, so ask for it before you plan a go-live date.

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Official Easybell networks

For UDP/TCP, Easybell publishes:
For TLS, Easybell publishes:
Choose the list that matches the transport configured at Easybell. These are signaling sources for the receiving system, not outbound platform addresses.

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Transferring calls

Cold transfer uses SIP REFER through the provider of the current call. Confirm that your exact Easybell product supports the intended destination. A 405 response means the method was rejected; changing the phone-number format does not enable REFER. For a new outgoing connection, use Warm Transfer and select the Outbound phone number to use. This can be a platform number even when the incoming call uses Easybell. If you select Easybell for the outgoing leg, its outbound authentication must work first.

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Validate the setup

Save the exact DID and source addresses, assign the number to an assistant, and call it externally. Confirm a new inbound call, the correct assistant, and two-way audio in History. Sources: Easybell FQDN authentication, Easybell Cloud PBX FQDN resource, Easybell Trusted IP. Accessed 22 August 2026.

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Outbound SIP identity

Easybell requires the SIP authentication username in the outbound From user. If it differs from your public phone number, choose SIP username under Outbound SIP identity. Keep Phone number (DID) and your public number. Match Caller ID source to the field selected in the Easybell caller ID settings. Do not replace the DID with the username or add a custom From header. Easybell SIP authentication · Easybell caller ID settings