---
title: What to do if carrier blocking is suspected
description: Contact us to review delivery failures that may involve a carrier’s blocking system.
---

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# What to do if carrier blocking is suspected

## Contact us to review delivery failures that may involve a carrier’s blocking system.

A phone carrier may block a fax call if its systems identify the traffic as unwanted. However, a failed fax by itself doesn’t confirm that blocking is the cause.

First, check the fax’s result in **Outbox** and confirm that the destination number is correct.

If failures continue and blocking is suspected, let us know:

- The sending and receiving fax numbers.
- The date, time, and time zone of a recent attempt.
- The failure message.
- Whether the issue affects one destination or several.

Please provide an example from the last 24 hours when possible.

We can review the available information and explain the next step. If a carrier requires an unblocking request from your organization, we’ll explain what you need to provide.

Keep recipient numbers current and honor requests to stop sending. Before changing your fax line’s calling number, also called **ANI**, let us review the issue with you.

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