When Microsoft Teams Phone shows Error Code 480, the most useful public Microsoft mapping is Microsoft response code 10037, which means No callee endpoints were found. In plain words, Teams tried to deliver the call but could not find a reachable client endpoint for the person or destination it was supposed to ring. [✅Source-1]
At the SIP level, 480 means Temporarily Unavailable. The standard uses it for cases where the callee is not logged in, is signed in but cannot take the call in the current state, has a status that blocks communication, or has no valid forwarding location at that moment. So the signal usually points to temporary reachability, not to a malformed number or a media codec mismatch. [✅Source-2]
Main Reading 480 sits on the callee availability side of the call path. Start with user reachability, then review call handling rules, and only after that move into Direct Routing telemetry and SBC inspection. Small detail, big time saver.
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What Error Code 480 Means in Teams Phone
Teams Phone 480 is not just a generic failure notice. It usually tells you that the call reached a point where endpoint discovery mattered, and the intended destination was not available in a way that allowed Teams to complete the ring path. Administrators often compare the situation with other documented Microsoft Teams calling error codes to confirm whether the failure relates to endpoint reachability, forwarding logic, or Direct Routing behavior. Put simply, the call knew where it wanted to go; it just could not find a live place to land.
What the Code Is Telling You
- Signaling got far enough for the callee side to matter.
- The destination was temporarily unavailable, not permanently missing.
- A reachable Teams endpoint was not found for the final ring target.
What You Should Not Assume Yet
- Not every 480 is a firewall problem.
- Not every 480 is a dial plan error.
- Changing audio devices first is usually too early.
Where the Failure Usually Starts
No Active Teams Endpoint
The most common reading is still the simplest one: the intended user has no active, reachable Teams client endpoint. A stale sign-in, a desktop session that never refreshed cleanly, or a user who expects calls to ring on one device while only another device was previously registered can all leave the final destination effectively unavailable. That is why sign out, sign back in, and test again is still one of the fastest first moves.
Call Handling Rules and Delegation
Call forwarding, simultaneous ringing, unanswered routing, and delegates all change the final delivery path. In the Teams admin center, these settings live under the user’s Voice options, and the page also notes that if the Voice tab is missing, the user does not have a Teams Phone license assigned. Review these rules carefully. Often, the original callee is fine, but the ring path has been redirected somewhere that is not actually available. [✅Source-3]
- Check whether the call should ring the user first, or a forwarded destination first.
- Verify unanswered rules and ring timeout values.
- Review delegates and call group targets that may now be outdated.
- Confirm the final target is still a valid, reachable Teams endpoint.
Direct Routing Delivery Path
If the tenant uses Direct Routing, the delivery path includes the Session Border Controller, Direct Routing components in Microsoft Cloud, and telecom trunks. Microsoft also documents that SBC health is watched through SIP OPTIONS, sent every minute, and that Direct Routing uses those health signals during routing decisions. A route that looks fine on paper can still behave badly if one SBC is degraded, demoted, or pairing is unstable. [✅Source-4]
Practical Reading If 480 appears for one user only, begin with that user’s endpoint and call handling rules. If it appears across a route, site, or number range, shift faster toward Direct Routing, SBC health, and call flow evidence.
Checks That Make Sense on the User Side
Teams already exposes the most useful end-user checks in a few places: Settings > Calls for call handling and voicemail, Manage delegates for shared line behavior, and Settings > Devices for a test call. Use those screens before changing tenant-wide settings. They are close to the symptom, and close is good. [✅Source-5]
- Open Settings > Calls and inspect call handling, forwarding, simultaneous ring, voicemail, and delegate settings.
- Open Settings > Devices and run a test call. This does not validate an SBC route, but it does confirm that the local Teams client is alive and that the device path is not broken at the desktop level.
- Sign out of Teams on the main device, sign back in, and place a fresh call.
- If the user expects calls on mobile as well, verify the intended device is actually signed in and receiving notifications.
- If the line is shared, confirm the delegate relationship still matches the real call flow the team wants.
A Good Shortcut When a user says, “It rings nowhere,” look first for endpoint reachability. When the user says, “It rings the wrong place,” look first for call handling rules.
Checks That Matter in the Admin Center and SBC
The PSTN usage report is one of the most useful places to start. Microsoft states that the Direct Routing tab shows call start and end times, SIP address information, and SIP call flow data that helps diagnose issues between the organization’s SBC and Microsoft SIP Proxy. That gives you a stable starting point before you touch routes or trunks. [✅Source-6]
Once you are inside the call record, the SIP call flow view shows the chronological exchange between the SBC and Microsoft SIP Proxy. Microsoft notes two limits that save a lot of confusion: call data can take up to 30 minutes to appear, and records older than 30 days are not available in that view. If an admin checks too early or too late, the evidence may seem to “disappear” when it never had a chance to appear in the first place. [✅Source-7]
- Confirm the user has a valid Teams Phone assignment and the expected voice settings.
- Open the call record in the Direct Routing report.
- Check the final SIP result and read the ladder, not just the label.
- Compare the failing call with a successful call from the same route.
- Only after that, change routing elements or SBC behavior.
For route-wide issues, Microsoft’s Direct Routing monitoring notes are blunt and useful: Call Analytics helps after calls reach internal Direct Routing components, but if pairing is wrong or the SIP INVITE is rejected early, SBC logs matter more. The same page also states that an SBC is treated as healthy when OPTIONS arrive every minute and have been seen within the last three minutes. So yes, a route can look present yet still be a poor candidate at call time. [✅Source-8]
Network and SIP Data Worth Checking Before You Rule Anything Out
Not every 480 is network-caused. Still, a weak or blocked path can make the destination look unavailable. Microsoft’s network planning numbers for Teams audio are concrete: 10/10 Kbps minimum, 58/58 Kbps recommended, and 76/76 Kbps for higher-quality conditions, measured per endpoint. That gives you a clean baseline when one device behaves differently from another on the same account. [✅Source-9]
| Teams Audio Bandwidth Level | Upload | Download | When It Helps |
|---|---|---|---|
| Minimum | 10 Kbps | 10 Kbps | Basic survivability check |
| Recommended | 58 Kbps | 58 Kbps | Normal voice calling conditions |
| Higher Quality Target | 76 Kbps | 76 Kbps | Cleaner, more stable audio delivery |
For the Teams client path, Microsoft lists the main connectivity requirements as TCP 80 and 443 plus UDP 3478, 3479, 3480, and 3481. The same page labels those UDP ports by function: 3478 for STUN, 3479 for audio, 3480 for video, and 3481 for sharing or VBSS. If those paths are blocked or mangled, endpoint reachability becomes harder to trust. [✅Source-10]
For Direct Routing without media bypass, Microsoft documents media processor port ranges of 3478–3481 and 49152–53247, and it recommends at least two ports per concurrent call on the SBC. That is a small line in the documentation, yet it matters. Port exhaustion, poor SBC sizing, or firewall rules that only partly match the route can leave a call looking “temporarily unavailable” even when the dialed destination is correct. [✅Source-11]
Useful Distinction 480 is a signaling result, but signaling does not live in a vacuum. If the client, SBC, or Microsoft path cannot maintain the expected route and port behavior, the final ring target can look unavailable even when the account itself is valid.
A Diagnostic Order That Saves Time
- Read 480 as a destination availability problem first.
- Check whether the user had an active Teams endpoint at the moment of failure.
- Review forwarding, unanswered routing, simultaneous ring, and delegates.
- If Direct Routing is in play, open the call record and read the final SIP code plus ladder sequence.
- Check whether the issue is isolated to one user, one number pattern, one route, or one SBC.
- Only after that, review ports, SBC health, and route design.
That order works because it follows the same path the call followed. First the endpoint, then the ring logic, then the route. Reverse that order, and hours disappear.
FAQ
Is Microsoft Teams Phone Error Code 480 the same as a full service outage?
No. It usually points to temporary callee unavailability or a missing reachable endpoint for the final destination. A tenant-wide outage can create similar symptoms, but 480 by itself is narrower than that.
Does Error Code 480 always mean the user is signed out?
Not always. A signed-out client is a common reading, but the SIP standard also uses 480 for other temporary states where the callee cannot take the call or has no valid forwarding location at that moment. In Teams public troubleshooting material, the well-known mapping is still No callee endpoints were found.
Can forwarding or delegate settings play a part in a 480 result?
Yes. Those settings change where the call actually tries to ring. If the redirected destination has no valid, reachable endpoint, the original caller may only see the final 480 result and not the path change that caused it.
Where should an admin look for the final SIP result first?
Start with the PSTN usage report for Direct Routing calls, then move into the SIP call flow. The ladder view is far more useful than a single label because it shows where the path stopped making progress.
How long does it take before SIP call flow appears in Teams admin reporting?
Do not expect it instantly. Microsoft states that processing can take up to 30 minutes, and the SIP call flow view does not keep records older than 30 days.
Should I change SBC routing before checking the user account?
Usually no. When a 480 affects one person, user endpoint reachability and call handling rules are the faster first checks. When the same result hits many users on the same path, then SBC health, route logic, and port behavior move much higher on the list.