Whenever I send an email to a customer, the email is sent in plain text even though I have specified in my configure->email options for the email to be sent in html. The administrator email however is sent in html. What I want is for all emails to be sent in html format. Here are some of the specifications that I have on my server.

PHP Version 4.4.1
MySQL 5.0.54
Zen Cart 1.3.8a
HTTP Server: Microsoft-IIS/6.0

Configure->Email Options:
Use MIME HTML when Sending Emails: true
Send Emails: true
Email Archiving Active: true
Email Admin Format: HTML
Email Transfer Method: SMTP

Configure->Customer Details
Customer Default Email Preference: HTML