Thanks for joining the thread, @Khelzor. I'm here to help you fix the winmail.dat issue in QuickBooks.
Recipients of files sent through QuickBooks receive an attachment called Winmail.dat instead of a .pdf file. This happen when recipient's email client is not capable of receiving rich text format (.rtf).
To fix this, you'll have to change the message format in Outlook and choose either HTML or plain text to prevent Outlook from attaching a Winmail.dat file when sending an email. Also, you can use other email than Outlook. For more details, see this article: Winmail.dat is attached to email instead of a .pdf file when sent from QuickBooks through Outlook.
Furthermore, here are some resources on how to customize email templates and use them to send messages from QuickBooks:
I'm just a few clicks away if you have any other questions. I'll make sure you're taken care of. Stay safe.
