simple mail() question

Hello All, I have a simple mail() question, and I hope a hero can shed some light. I can't understand why my messages are being encoded, and extra headers are being added, *before* the message is sent through sendmail. Infinite Thanks, Adam Input: $more test.php <? $header = "Content-Type: text/plain; charset=us-ascii"; mail('joe@test.com', 'subject', 'body', $header); ?> Expected Result: $php -d sendmail_path=/bin/cat test.php To: joe@test.com Subject: subject Content-Type: text/plain; charset=us-ascii body Actual Result: $php -d sendmail_path=/bin/cat test.php To: joe@test.com Subject: subject Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: BASE64 Ym9keQ==