PHP mail only showing first word of from name

I have this for:

DEFINE ('EMAIL_HEADER', 'From: Our World noreply@xxxxx.com' . "\r\n" . 'Reply-To: info@xxxxx.com' . "\r\n" . 'X-Mailer: PHP/' . phpversion());

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For this:

$sent = mail($current_email, 'xxxxx xxxxx Account Activated', $body, EMAIL_HEADER);

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But the from is only show from Our, if I put it in quotes it shows as  "Our World".

Can you see what I'm doing wrong?  I just want it to be from Our World