PDF Form javascript submission - email format

I suspect this is out of my control but I'm being told by end user that when they try to submit the form the email that's popping up is in plain text but they need it to generate in html format - this is primarily so that the user signature adds automatically (assuming it is set up that way) to the email.

Is there any way to do this? Or is it a local setting I can't affect?

The code attached to the submit button checks required fields then, assuming they're complete, creates email, cc'ing up to two people who add their details to the form:

var requiredFields = new Array();
for (var i = 0; i < this.numFields; i++)
{
var fName = this.getNthFieldName(i);
var f = this.getField(fName);
if (f.type!="button" && this.getField(fName).required && (this.getField(fName).value == null || this.getField(fName).value == ''))
{
requiredFields[requiredFields.length] = fName;}}
var error = "Please complete the following fields: \n\n";
for (j=0; j < requiredFields.length; j++)
{
if (requiredFields[j].value == null)
{
error = error + requiredFields[j] + '\n';
var f2 = this.getField(requiredFields[j]);
f2.setFocus();
}

}

if (requiredFields.length > 0) {
app.alert(error);
} else {

var cToAddr = "email@companyname.co.uk";
var cCCAddr = this.getField("Email1").value;
var cArAddr = this.getField("Email2").value;
if(cArAddr != "")
cCCAddr += ";" + cArAddr;
var cSubLine = "New request form";
var cBody="Generic message here.";

this.mailDoc({bUI: true, cTo: cToAddr, cCc: cCCAddr, cSubject: cSubLine,cMsg:cBody});
}