Why Your CLI is Getting Blocked and How to Fix It

CLI blocking is one of the biggest challenges in outbound calling. Learn the common reasons your Caller ID gets blocked or spoofed, and proven strategies to maintain delivery.

Why CLI Gets Blocked

CLI (Caller Line Identification) blocking happens when telecom carriers or spam filters reject or modify your outgoing Caller ID. Here are the main reasons:

1. High Call Abandonment Rates

If a large percentage of your outbound calls are abandoned (hung up before answering), spam detection systems flag your number.

Fix: Keep abandonment rates under 3%.

2. Using Non-Allocated Numbers as CLI

If your Caller ID is a number that doesn't actually exist or isn't assigned to you, carriers will reject it.

Fix: Only use DIDs that you own and have purchased from HexaVoice.

3. Call Volume Spikes

Suddenly sending 1,000 calls per hour from a single number triggers fraud detection.

Fix: Use number rotation. HexaVoice supports caller ID pools — distribute calls across multiple DIDs.

4. Calls from Blacklisted IP Ranges

If your SIP traffic originates from an IP range that's been blacklisted (common with shared hosting), CLI may be stripped.

Fix: Use HexaVoice's dedicated IP allocation. Contact support to get a dedicated origination IP.

5. Regulatory Compliance Issues

In some countries (US, UK, EU), CLI must match a registered business number. Using fake CLI is illegal.

Fix: Register your business numbers. In the US, use STIR/SHAKEN compliant CLI numbers.

STIR/SHAKEN — What It Means for You

STIR/SHAKEN is a US regulatory framework that cryptographically signs caller IDs to verify their authenticity. Calls without proper attestation may be labeled "Spam Likely" by mobile carriers.

HexaVoice supports STIR/SHAKEN for US origination numbers. To enable:

Go to Dashboard → SIP Trunks → CLI Settings
Enable "STIR/SHAKEN Attestation"
Submit your business verification documents

CLI Whitelisting at HexaVoice

HexaVoice maintains relationships with tier-1 carriers globally. When you:

Purchase a DID from HexaVoice
Register it as your outbound CLI
Enable CLI whitelist in your trunk settings

Your number is actively whitelisted with our carrier partners, significantly reducing CLI blocking rates.

Practical CLI Maintenance Tips

Rotate your CLI numbers regularly (use at least 3-5 numbers per campaign)
Monitor answer rates — below 30% ASR often signals CLI blocking
Never reuse a number that has been flagged as spam
Use local DIDs matching the region you're calling
Keep call volume per number under 200 calls/day initially