Convert plain text file to HTML and send email from Windows server.

We currently have an application that generates text files that needs to be sent as an HTML rendered email. The application cannot do this natively. The server producing this text file is 'offline' so it doesn't have traditional access to the internet. We're currently just opening a port and using Powershell to send the text file out to another application, Zapier. We want to eliminate Powershell and Zapier. The Powershell commands are eating through CPU resources and we haven't set up all the emails yet, so that isn't a viable solution even short term. In a perfect world, there would be a way to convert the generated plain text (always in the same folder, but the file name reflect the date/time) to HTML and send them to the appropriate recipient (which is auto generated within the text file).