Keep Coding

I am just developing my first simple app. It generates and sends an HTML formatted email to my customers who have just purchased a product. It sends email using Intent:
Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND);
emailIntent.setType("text/html");
emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL, new String[] {email});
emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,Html.fromHtml(htmlcode));
thiscontext.startActivity(Intent.createChooser(emailIntent, "Send mail..."));
This works great if I send the email using Gmail, but I cannot find any other email client that will send an HTML formatted email. Some will be text, some will be blank. Have tried K-9, Droidmail, Innomail, android default email and others.
The thing is that I do not want to send from my Gmail account. Why do none of these work, and does anyone know of an email client that will work correctly?
Cheers