The email configuration experience enables users to be more effective and efficient when using email to communicate with customers. To change the default font properties of email body, we can use an existing web resource file (JScript) by the following approach:
- Configure the web resource file
- Enable the RTE control in the email form
1. CONFIGURE THE WEB RESOURCE FILE: NAVIGATION STEPS: Step 1: Navigate to Advanced Settings -> Customize the system -> Web Resources. Step 2: Use the custom filter on display name to search for the web resource as shown below 
Step 3: There may be more than one file named msdyn_EmailRTEConfig.js. One is the default, out-of-box configuration file that isn’t modifiable. The other one can be opened and used as a reference to create a new web resource file that will host our configuration changes. Note: There may be only one file available and if we check the description of the file, it should be editable as shown below: 
Step 4: Open the web resource, select Text Editor and Edit Content window will be displayed. 
Step 5: Copy the text from the Source area, and then close the window. Step 6: Create a New Web Resource and paste Source content in New Web Resource. Step 7: Make the font changes you want, and then select Save and publish. Step 8: Save the URL of the new web resource because we’ll need it to map the new web resource file to the Email form. 
2. ENABLE THE RTE CONTROL IN THE EMAIL FORM NAVIGATION STEPS: Step 1: Navigate to Customization -> Customize the System -> Entity -> Email -> Forms. Step 2: Open the Email Form and Double Click on Description field to open field Properties. 
Step 3: Select the Controls tab and add RTE (Rich Text Editor) control. Step 4: Edit the Custom Configuration URL as shown below. 
Step 5: Replace singleLine.URL with the web resource URL of the newly created web resource file we created in the steps above. 
Step 6: Save and Publish. Output: Before the update of the above Configuration 
After the update of the above Configuration 