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How to Prevent Email Attachments from Appearing as Winmail.dat Files in Outlook?

At BlueMail, we understand the frustration of receiving email attachments as winmail.dat files, which are difficult to open in non-Outlook email clients. This common issue occurs because Outlook uses a proprietary email format. To help your contacts send you attachments in a more accessible format, we’ve provided a guide they can follow to adjust their Outlook settings.

For Outlook 2016 and Later:

  1. Open Outlook and click on File.
  2. Select Options.
  3. Go to the Mail category.
  4. Under Compose messages in this format, ensure HTML or Plain Text is selected.
  5. Under Message format, make sure Convert to HTML format or Convert to Plain Text format is selected for When sending messages in Rich Text format to Internet recipients.
  6. Click OK.

For Outlook 2002 to 2007:

  1. Select Tools > Options... from the menu.
  2. Go to the Mail Format tab.
  3. Under Compose in this message format, select either HTML or Plain Text.
  4. Click Internet Format.
  5. Ensure Convert to Plain Text format or Convert to HTML format is selected under When sending Outlook Rich Text messages to Internet recipients, use this format.
  6. Click OK.
  7. Click OK again.

For Outlook 2007 to 2013:

  1. Search for the contact in your Outlook Contacts.
  2. Double-click the contact's email address.
  3. Alternatively, right-click the desired email address and select Open Outlook Properties or Outlook Properties from the menu.
  4. Under Internet format, select either Let Outlook decide the best sending format or Send Plain Text only.
  5. Click OK.

Additional Tips for Outlook 2016:

  • Ensure the Email Address is Not in Your Outlook Contacts:
    • Outlook 2016 does not offer a way to change sending preferences for email addresses assigned to an address book entry.
  • Right-Click Method:
    • Open an email from the desired email address or start a new message to it.
    • Right-click on the address.
    • Select Outlook Properties from the menu that appears.

Senders can ensure their email attachments are compatible with a variety of email clients, including BlueMail. Sharing this guide with your contacts can help eliminate the inconvenience of winmail.dat attachments, allowing for a smoother communication experience.