Create a script (it can be in outlook) that converts the Plain Text email to an Html email (template) and enables the auto-forward of this email for some people

I have a system of instructions that is sent daily in my clients' emails, the emails are all in the same pattern. The problem is that the program that sends these emails only allows Plain Text. So my idea was to provide a better design in html, so that when I receive the email in plain text, it is converted to the design in html and automatically sent to my clients with the new format.