Model the number, inbound trunk and outbound authorization separately
Record the account, Yay.com number, number-to-trunk assignment, inbound identity choice, destination address or FQDN, port, transport, outbound authorized source addresses or username and password, and the matching PBX objects. The dashboard requires the number to be assigned to the trunk before that trunk becomes its inbound route.
A working outbound call or accepted source address does not establish number assignment, destination reachability or the identity delivered to the PBX. Likewise, an inbound INVITE does not prove outbound authorization.
Documented service facts
Reviewed 2026-10-18. Compare SIP trunk services →
SIP authentication
DocumentedOutbound calls can be authorized by one or more approved public PBX addresses, optionally with username and password. Inbound delivery separately identifies requests by the dialled number or a configured trunk username. Preserve direction, portal object, source, delivered identity, challenge and observed result.
SIP registration
DocumentedThe general workflow documents source-IP outbound authorization without a REGISTER dependency and optional credentials, while the public FreePBX example also shows a registered credential path at talk.yay.com. Determine the selected account mode and keep REGISTER, challenge, INVITE and completed call as separate evidence.
Inbound delivery and number format
DocumentedA Yay.com number must be assigned to the selected trunk. Inbound delivery targets a public address or FQDN, port and UDP, TCP or TLS transport and can present the dialled number or configured username using E.164 or GB national format. Preserve assignment, DNS, Request-URI, identity and PBX match.
Inbound resilience
Not verifiedThe product page describes combining hosted routing features with an on-premises PBX, but the reviewed trunk pages do not establish trunk-priority, health-check, automatic alternate-PBX delivery, detection or restoration semantics. Qualify any FQDN behavior, alternate call route, forwarding target, timing, caller identity, capacity, charges and return-to-primary path separately.
Number and regional availability
Not verifiedYay.com markets UK business numbers and documents number transfer, but the reviewed trunk pages do not prove that every number type, rate centre, address, existing number or requested port is available on a given date. Obtain a dated inventory or port result for the exact account, legal entity and service address.
Audio codecs and DTMF
DocumentedThe published FreePBX example lists µ-law, A-law and GSM with RFC 2833 DTMF; a Grandstream example elsewhere in the same help set recommends G.722, PCMA and PCMU. These device examples are not a universal trunk contract. Preserve the actual SDP offer and answer, packetization, telephone-event mapping, RTP endpoints and decoded result.
Fax and T.38
Not verifiedThe business page mentions Email to Fax as a hosted feature, but the reviewed SIP-trunk sources do not establish T.38, audio-fax fallback, direction, gateway interoperability or document limits for the PBX trunk. Qualify trunk fax and any hosted fax service as separate products with an approved representative document set.
Signaling and media encryption
DocumentedYay.com documents TLS signaling and SRTP media. Its inbound guidance requires SRTP to agree in the dashboard and endpoint and warns that a mismatch causes call problems. Verify certificate validation, SDP, negotiated media profile and each packet direction; do not infer complete-path encryption.
Concurrent calls and call-start rate
Not verifiedThe current voice-plan comparison lists SIP trunks as unlimited, while the trunk product page does not publish a per-account concurrent-call or calls-per-second entitlement. Do not convert the number of trunk objects, users or plan language into channel or CPS capacity. Obtain dated account limits and run a separately approved bounded load test.
Emergency calling
DocumentedYay.com exposes emergency-address records that can be assigned to numbers. That documents an administrative relationship, not successful routing, dispatchable-location validation or nomadic behavior for every trunk call. Confirm number ownership, registered address, site, callback path, presentation, outage alternative and the provider-approved test process; do not place an uncoordinated emergency call.
Pricing model
DocumentedThe trunk product page says incoming calls are not charged and outbound calls are charged, while the voice-plan page publishes hosted-plan prices and inclusions. Those pages do not establish a complete trunk quote, number rental, port fees, outbound destinations, taxes, support, renewal or cancellation for a specific account. Obtain a current written order before purchase.
Administration and support
DocumentedThe current dashboard workflow owns trunk destination, number assignment, inbound identity, number format, transport and outbound authorization. The public FreePBX page uses legacy chan_sip-style fields and is historical context, not a current FreePBX 17 PJSIP template.
SMS and MMS
Not verifiedThe reviewed SIP-trunk pages do not establish SMS or MMS eligibility, sender registration, API scope, throughput, retention or price for a trunk number. Qualify messaging as a separate number and commercial service rather than inferring it from voice routing or number assignment.
Preserve the inbound identity and number format actually selected
Yay.com lets inbound delivery identify the request by the dialled number or by a configured trunk username, while still passing dialled-number information. It also offers E.164 with a leading plus or GB national format. Preserve the selected controls and the actual Request-URI, To and asserted identity rather than broadening PBX patterns to accept every form.
Compare those values with the loaded PJSIP endpoint identification, context and first matching FreePBX inbound route. A request can reach the listener yet miss the intended route because the selected identity or format differs.
Treat IP delivery, FQDN resolution and registration as different evidence
The inbound destination can be a public address or FQDN with a selected port and UDP, TCP or TLS transport. Preserve the submitted destination, current DNS answers, TTL, chosen address, provider source, customer-edge receipt and listener. A saved FQDN is not proof of the address used for one call.
The general trunk workflow documents source-IP authorization for outbound calls and optional credentials, while the FreePBX example also shows a registered credential path at talk.yay.com. Determine the selected model before interpreting REGISTER or copying a template.
Prove TLS signaling and SRTP media independently
Yay.com documents TLS for SIP and SRTP for audio. For inbound SRTP, its guidance requires encryption to be enabled in both the endpoint and the Yay dashboard and warns that a mismatch causes call problems. Preserve the configured hostname, certificate chain, TLS session, SDP offer and answer, negotiated media profile, RTP directions and decoded audio.
A successful TLS session does not establish SRTP negotiation or two-way audio. The customer-facing encrypted leg also does not prove protection through every carrier, forwarded destination, recording system or endpoint.
Use published firewall inputs without converting them into packet evidence
The current firewall page publishes separate SIP and RTP source addresses plus signaling and media port guidance and says to disable SIP ALG when enabled. Record the exact dated source page, but compare it with DNS, the provider attempt, edge decisions and a narrow authorized capture.
Do not open the full Internet, accept anonymous SIP or assume every published address participated in one call. A permitted rule is not proof that a packet arrived, matched the intended PBX object or followed the negotiated media destination.
Keep the FreePBX example inside its driver and release boundary
The public Yay.com FreePBX example uses type=peer, insecure=port,invite, register strings and other chan_sip-style fields. Retain it only as provider terminology and historical screen context. Do not copy those fields into FreePBX 17 PJSIP without mapping them to the installed release and supported owners.
Make durable changes through current trunk, Asterisk SIP Settings and inbound-route controls, then inspect generated and loaded endpoint, identify, AOR, registration and transport state. Use the paired diagnostic to correct the earliest demonstrated mismatch.
Diagnose inbound identity and media without changing working outbound authorization
Use the Yay.com inbound diagnostic to trace number assignment, identity, destination, PBX matching, TLS, SDP and SRTP.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
- Yay.com Emergency Address API ↗
- Yay.com number-transfer requirements ↗
- Yay.com voice plans ↗
- Yay.com SIP Trunks for business phone systems ↗
- Yay.com create a SIP trunk ↗
- Yay.com SIP trunks and how to use them ↗
- Yay.com call encryption, TLS and SRTP ↗
- Yay.com firewall guide ↗
- Yay.com legacy FreePBX configuration example ↗
- Yay.com trunk-authentication API ↗
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.