cambia
# Check for Message Subject
if ($Config{'subject'}) { print MAIL "Subject: $Config{'subject'}\n\n" }
else { print MAIL "Subject: WWW Form Submission\n\n" }
Por
Código:
# Check for Message Subject
if ($Config{'subject'}) { print MAIL "Subject: $Config{'subject'}\n Content-type: text/html \n\n" }
else { print MAIL "Subject: WWW Form Submission\nContent-type: text/html \n\n" }
Probalo y decime...
Saludos