Description:
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I'm not sure if anyone else noticed this... I run php 4.3.2 on my windows xp pc with apache 1.3. I don't have a domain name, and while exploring options on how to send mail from my pc, I found out you could send email from any address to anyone else without knowing thier password. Eg/ I could send hate mail from you@example.com where my real address is me@example.com.

Reproduce code:
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<?php
ini_set("SMTP", "smtp.example.com");
ini_set("sendmail_from", "you@example.com");
mail("me@example.com", "Hate mail subject", "Body Text");
?>

Expected result:
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An email in my inbox from you.

Actual result:
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Same as above.