SIP 608 Rejected

What SIP 608 means

A network in the middle blocked the call before it reached the recipient, judging it unwanted. Unlike a 607 this is an automated decision rather than a person, and it is designed to carry a contact route so a wrongly blocked business can appeal.

Global failure (6xx)
Sent by An intermediary blocking on the recipient behalf
Occasional

What SIP 608 Rejected actually means

An intermediary rejected the call on the recipient behalf, and the response can carry a Call-Info header pointing at a means of contesting the block. That appeal route is the whole point of the code: it exists so legitimate callers caught by automated blocking have somewhere to go.

What causes SIP 608 on a business phone system

An analytics service classified your number as nuisanceAutomated systems score numbers on calling patterns and user reports, and blocking happens before any phone rings. Businesses often discover it only when customers say calls never arrive.
The caller ID cannot be verifiedCalls presenting an unverifiable or inconsistent CLI are more likely to be blocked automatically.
Your number shares a range with abused numbersReputation can attach to a range as well as a single number, so a clean number can inherit a problem.

How to fix SIP 608

Look for the appeal route in the responseWhere a Call-Info header is present it points at how to contest the block. Ask your provider to retrieve it from the SIP trace if you cannot see it yourself.
Check your number reputationLook up how your outbound number appears to recipients before assuming the problem is technical.
Raise it with your provider as a CLI reputation issueProviders can pursue delisting on your behalf, which is considerably more effective than changing numbers and waiting for the same thing to happen again.

Fixing the underlying problem

This page explains the code. These guides walk through the fix in detail.

Questions about SIP 608

My business calls are being blocked with SIP 608. What can I do?

A 608 means an automated system blocked the call before it reached the recipient, and the code is specifically designed to carry a route for contesting that. Ask your provider to pull the Call-Info header from a failing call, then pursue delisting through it. Check how your number is currently labelled at the same time.

What is the difference between SIP 607 and SIP 608?

Who made the decision. A 607 is a person marking your call as unwanted. A 608 is an intermediary blocking it automatically on their behalf, often before any phone rings, and it can include a way to appeal.

Related SIP response codes

Source. SIP 608 Rejected is defined in RFC 8688 and registered in the IANA SIP Parameters — Response Codes. The causes and fixes above are drawn from our own experience supporting UK business phone systems.

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