What does HRESULT 0x80EE0016 (RTC_E_INVALID_PROXY_ADDRESS) mean?

RTC_E_INVALID_PROXY_ADDRESS

What the RTC value marks: RTC_E_INVALID_PROXY_ADDRESS

This result belongs to the SIP transport and reachability boundary area of RTC and identifies the profile’s proxy address is syntactically invalid or unusable as a SIP next hop.

This result carries 0x80EE0016 in the RTC interface facility 0xEE; store the result value at the first RTC callback or method boundary, before retry logic replaces it with a broader timeout or connection message.

Start the result investigation by having the trace inspect proxy host, port, transport, URI scheme, and unauthorized whitespace or parameters; do not skip the distinction that the user destination may be valid even though the configured intermediary is not.

Protocol and object state

DNS discovery, socket establishment, proxy tunneling, and SIP transaction completion are distinct phases and should not be collapsed into one “network error”. A retry is safe only after the application identifies whether any request bytes were transmitted and whether the previous client transaction still exists.

Evidence that separates the cause

• Code-specific proof: inspect proxy host, port, transport, URI scheme, and unauthorized whitespace or parameters.
• Identity and target: proxy tunnel response.
• State at production: SIP transaction timer and retransmit count.
• Timing and ordering: original SIP URI and selected next hop.

A safe diagnostic sequence

1. Collect enough evidence to inspect proxy host, port, transport, URI scheme, and unauthorized whitespace or parameters.
2. Test the competing explanation explicitly, because the user destination may be valid even though the configured intermediary is not.
3. Apply the targeted fix — correct the proxy field and validate it before enabling the profile — and validate both protocol completion and object cleanup.

How to handle the result

The appropriate response to it is not a blanket reconnect. Instead, correct the proxy field and validate it before enabling the profile, while preserving ownership of cleanup and any bounded retry.

Example: A provisioning feed places an HTTP URL in the SIP proxy address field.

Actions that do not address this condition

• Do not retry rapidly across every resolved address without preserving the failure phase.
• Do not switch transports without checking profile policy and authentication constraints.

Related RTC results

Technical references

• Microsoft RTC return constants.
• SIP transport behavior.
• Locating SIP servers.
• SIP and TEL URLs in RTC.