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8x8 Support

Internet Fax Internal Conversion Error


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

Applies To

  • Work for Desktop
  • Work for Web
  • Internet fax


Ensure Compatible Attachment

8x8 Internet fax Supported File Types

  • .docx
  • .doc
  • .dotx
  • .rtf
  • .txt
  • .pdf (recommended)
  • .ppt
  • .html
  • .htm
  • .xls
  • .xlsx
  • .xlt
  • .csv
  • .bmp
  • .jpeg
  • .jpg
  • .gif
  • .tif
  • .tiff
  • .pct
  • .pcx
  • .png
  • .ras
  • .fax
  • .odt

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(s). Otherwise, proceed below for a detailed fix. This fix assumes a Windows environment. Click to download Adobe Reader.

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

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


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.

Please note that 8x8 Virtual Office 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 Virtual Office Desktop or Online.
  • Must use 11 digits (1 + 10-digit phone number) for sending outbound fax. Not doing so may result in a Number is Incomplete error.
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