Put very simply, you get four variables to work with.
mail($to, $subject, $message, $header);
See if you can stuff all this...
"Name: $name", "Date: $date", "Fax: $fax",
"Does this Proposal ?: $proposal",
"What is the purpose of this proposal ?: $purpose",
"What are the expected benefits of this proposal ?: $benefits",
"What areas of operation should this proposal apply to ?: $areas",
"What are the time related factors of this proposal ?: $time",
"How should this proposal be undertaken ?: $undertaken",
"What are the expected outcomes of this proposal ?: $outcomes",
"What are the cost and saving estimates of this proposal ?: $cost",
"Is there any safety issues concerning this proposal ?: $safety",
"What is the impact on other equipment this proposal is related to ?: $impact",
"From: $email
...into the $message variable.