How HOTMAIL authenticate received messages?

Does anyone know which mechanism does HOTMAIL use to authenticate received emails? Recently I received in my inbox a spam from And tried to reproduce it by sending the following SMTP message to HOTMAIL, but although HOTMAIL queued for delivery, it never showed up in my inbox. Could HOTMAIL be comparing the IP address of the sender with the address returned by a DNS query for the mail server of the sender's domain (nslookup -querytype=mx viff@org) stated in the EHLO header to authenticate these messages? In this case a spam sent from the email server would go through. While another spam send from another domain, but claiming to come from would be blocked? If so, is there any documentation on the net about it?

Thanks in advance,


************************************************ andre@kirchner:~$ telnet 25 Trying Connected to Escape character is '^]'. 220 Sending unsolicited commercial or bulk e-mail to Microsoft's computer network is prohibited. Other restrictions are found at
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will result in use of equipment located in California and other states. Sat, 2 Feb 2008 12:16:29 -0800

EHLO ( Hello [] 250-SIZE 29696000 250-PIPELINING 250-8bitmime 250-BINARYMIME 250-CHUNKING 250-AUTH LOGIN 250-AUTH=LOGIN 250 OK


250 OK


250 my


354 Start mail input; end with . From: To: Subject: SMTP test

SMTP test body

. 250 Queued mail for delivery


221 Service closing transmission channel Connection closed by foreign host.


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