Introduction

If you received the error message "Unsupported Attachment: winmail.dat" in BillBjorn, it means that Microsoft Outlook sent an attachment in a format that BillBjorn does not support. This issue is caused by your Outlook email configuration. In this article, we'll explain why this happens and how you can fix it to ensure attachments are received correctly.


Why Am I Getting the "Unsupported Attachment: winmail.dat" Error?

The winmail.dat file is a Microsoft Outlook-specific attachment that appears when emails are sent in Rich Text Format (RTF) instead of Plain Text or HTML. Outlook converts formatting and attachments into this proprietary format, making them unreadable by most email clients, including BillBjorn.

If you send invoices or documents via email and they appear as winmail.dat, it is due to your Outlook settings.


How to Fix This Issue in Outlook

To ensure attachments are correctly received in BillBjorn, follow these steps to adjust your Outlook settings:

  1. Open Outlook.

  2. Go to File > Options > Mail.

  3. Under "Compose messages," change the format to either "HTML" or "Plain Text."

  4. Scroll down to the "Message format" section.

  5. Find "When sending messages in Rich Text format to Internet recipients" and set it to "Convert to HTML format" or "Plain Text format."

  6. Click OK to save the changes.

By making these adjustments, Outlook will send attachments in a universally compatible format, preventing them from being converted into winmail.dat.


What to Do if It’s Still Not Working

If you’ve made the changes to your Outlook settings and are still encountering issues, here are some additional steps to double-check:

  1. Restart Outlook: After updating your settings, restart Outlook to ensure the changes take effect.

  2. Clear the Cache: In Outlook, go to File > Options > Mail > Empty Auto-Complete List to clear any cached email settings that might be causing the issue.

  3. Test Sending to Yourself: Try forwarding the email to your own address, but use a non-Outlook email account, such as Gmail, to confirm that the attachment appears correctly.


If these steps do not resolve the issue, contact your IT support team for further assistance.