Saunders Technical Support

Thunderbird is not always able to open attachments from emails that were created in Outlook. Because of this issue, a lot of Thunderbird users see attachments come across as winmail.dat. The original attachment is embedded in this file, but Thunderbird does not know how to open it. There is an Add-on that can be installed onto Thunderbird that will allow users to open the winmail.dat file and retrieve the original attachment.

Start by going to https://addons.mozilla.org/en-US/thunderbird/addon/4433 to download the Lookout Add-on. Download the file to somewhere you can retrieve it later.

Open Thunderbird if it is not already.
Click on Add-ons under the Tools menu.



Click on the Install button to install the Lookout Add-on.



Find the file you downloaded and select it. Click Open and Thunderbird will install the Add-on.



Once the Lookout Add-on is installed, you will be required to restart Thunderbird. Once restarted, Thunderbird will automatically be able to open winmail.dat files correctly and display the missing attachments with the message.