---
title: "Internet Fax Internal Conversion Error"
slug: "internet-fax-internal-conversion-error"
updated: 2026-04-20T13:39:07Z
published: 2026-05-21T21:29:12Z
canonical: "help.8x8.com/internet-fax-internal-conversion-error"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.8x8.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Internet Fax Internal Conversion Error

## Symptom

Outbound fax attempts using 8x8 Work for Desktop or Online fail. After two to three minutes, the following error is received: *Internal Conversion Error*.

## Applies To

- 8x8 Work for Desktop
- 8x8 Work for Web
- Internet Fax

## Resolution

### Ensure Compatible Attachment

**Supported Filetypes**

| **BMP** | (Image) Bitmap Image File |
| --- | --- |
| **CSV** | (Text) Comma-Separated Values |
| **DOC** | (Text) Microsoft Word Document (Legacy) |
| **DOCX** | (Text) Microsoft Word Document |
| **DOTX** | (Text) Microsoft Word Template File |
| **JPEG** | (Image) Joint Photographic Experts Group Image |
| **JPG** | (Image) Joint Photographic Experts Group Image |
| **ODT** | (Text) Open Document Text File Format |
| **PCX** | (Image) Picture Exchange File |
| **PDF** | (Text) Portable Document Format |
| **PNG** | (Image) Portable Network Graphic |
| **PPT** | Microsoft Power Point Presentation file |
| **RAS** | (Image) SunOS Raster Graphic |
| **RTF** | (Text) Rich Text Format |
| **TIF** | (Image) Tagged Image Filet Format |
| **TIFF** | (Image) Tagged Image Filet Format |
| **TXT** | (Text) Standard Text Document |
| **XLS** | (Spreadsheet) Microsoft Excel Binary File (Legacy) |
| **XLSX** | (Spreadsheet) Microsoft Excel Binary File |
| **XLT** | (Spreadsheet) Microsoft Excel Template File |

### Correct PDF Digital Signature

*If you are familiar with working with digital signatures, a simple workaround is to remove the digital signature(s) and instead insert a signature image in the PDF on the appropriate line. Otherwise, proceed below for a detailed fix. This fix assumes a Windows environment. Select to* [*download Adobe Reader*](https://get.adobe.com/reader/)*.*

1. Open the PDF file in **Adobe Reader** or **Acrobat**.
2. From the menu, select **Edit** > **Preferences**.
3. From the left-hand menu, select **Signatures**.
4. Under **Identities & Trusted Certificates**, select **More**. The **Digital ID and Trusted Certificate Settings** pop-up will open.
5. Select **Add ID**.
6. Select **A new digital ID I want to create now**, then select **Next**.
7. Select **Windows Certificate Store**, then select **Next**.
8. Enter your identity information, then select **Finish**.
9. Close the **Digital ID and Trusted Certificate Settings** window.
10. In the **Preferences** window, select **OK**.
11. **Save** PDF file to apply changes.
12. Add the attachment to your fax and send.

> [!NOTE]
> Note:
> 
> It may take some extra time to prepare and send the fax, especially if the attachment is large.

## Cause

**One or more of the following is likely to be the case:**

- The attached file is not in a supported format. PDF is often the most reliable, so it is suggested that document attachments be converted to PDF before attempting fax. See supported attachment file types below.
- The PDF file attachment may contain a digital signature that may not have a trusted valid certification, which can also create the issue.

**Note that 8x8 Work faxing also has the current limitations:**

- Total fax size sent cannot be greater than 19 MB.
- Maximum of 5 files per fax.
- Maximum page count of fax attachment in fax email notification is 20 pages.
  - Internet fax notification with attachments are only available with faxes up to 20 pages (inbound only).
  - Any fax exceeding 20 pages can still be downloaded from 8x8 Work for Desktop or Web.
- Must use 11 digits (1 + 10-digit phone number) for sending outbound fax. Not doing so may result in a *Number is Incomplete* error.