Running Thunderbird 128.2.3esr (64-bit) on Ubuntu 24.04. In '''Settings > Filed & Attachments''', the '''pdf content''' type is set to Use System Handler (default). # Compose a message, add a PDF as an attachment, and save the message as a draft. # Go to the Drafts folder, select the message you saved, and double-click the attachment. The default helper application opens the file. # In the Drafts folder, double-click the message to open it, and then double-click the attachment. The following message appears: Double-click the attachment. The message /path/Downloads/thunderbird.tmp/nsmail.pdf could not be opened, because the associated helper application does not exist. Change the association in your preferences. Why can I open an attachment from a message in the Drafts folder, but not from the message itself?