Why Is Email From a Hotmail.Com or MSN.Com Account Rejected?

There are various anti-spam measures that can be employed to limit spam. None are likely to block all spam from your inbox and all are likely to come with some risk that legitimate email will be blocked as well. When a legitimate email is blocked as spam, the block is considered to be a "false positive".

This email server like many others uses DNS blacklists, aka blocklists, to attempt to limit spam coming into users' inboxes. Every system transmitting data over the Internet has an Internet Protocol (IP) address assigned to it. This address is commonly assigned by an Internet Service Provider (ISP). For home users it is unlikely to be a fixed address and may be different each time you connect to the Internet or is at least subject to change frequently.

When two email servers communicate with one another, each must know the other's IP address in order to send information and respond to one another. Some organizations maintain lists of IP addresses from which their email servers or others' email servers have received spam. Those lists are constantly updated as the systems sending spam continually change. Many of the organizations maintaing such lists make their lists available to others in a communal effort to combat spammers. System administrators of email servers may choose to use one or more such lists to limit spam coming into their own servers.

Each time an email message arrives, the IP address of the sending system is checked against any blacklists employed by the receiving email server. The receiving email server will contact a Domain Name System (DNS) server of the organization providing a blacklist used by the receiving email server with the IP address of the system attempting to send email to that receiving email server. If the DNS server indicates the sending server's IP address is on a blacklist, any email from that system will be rejected by the receiving email server.

One blacklist is the Spam and Open Relay Blocking System (SORBS). Unfortunately, at least several of Microsoft's Hotmail email servers are currently on a SORBS blacklist. Since email from MSN.com email addresses is also sent by Hotmail.com servers, email from an msn.com email address may also be rejected.

1. Why are Microsoft's hotmail.com email servers on the blacklist?
   
   Servers are added to the blacklist when spam is spam is detected emanating from those servers by blacklist maintainers.


2. Can you remove the Hotmail servers from the blacklist?
   
   No, the server owner, in this case Microsoft, will need to address the problem with SORBS.


3. The person sending to me reports that he or she can successfully send email to others, but not me. Why is that true?
   
   Email servers use different techniques to combat spam. Some system administrators for email servers employ blacklists while others employ different methods. And, among those employing blacklists, not all use the same blacklists. The SORBS list is widely used, but certainly not universally used. It is considered to be more "aggressive" in blocking spam than some other lists, though there are others which are even more agressive in how they deal with spam.


4. The hotmail.com sender reports that email to others is sometimes blocked as well. How can a Hotmail user determine if her email was blocked by a server using the SORBS blacklist or for some other reason?
   
   

   With the default Hotmail account settings, you won't see the reason the mesage bounced listed. To see the reason for the message rejection, you have to take the following steps while logged into your Hotmail account.

   1. While checking your inbox, click on "Options", which is next to "Help" at the top of the Hotmail webpage.
   2. Click on "Mail Display Settings".
   3. Change the "Message Headers" setting from "Basic" to "Advanced".
   4. Click on "OK".
   5. Go back to your inbox and hit the Refresh button in your browser to reload the message for which you wished to determine the cause of the message being rejected.
   6. Within the message you will now see a "View E-mail Message Source" link. Click on it.
   
   

   You should now see something akin to the following in the message.

   Final-Recipient: rfc822;test12345@moonpoint.com
Action: failed
Status: 5.7.1
Diagnostic-Code: smtp;550 5.7.1 <test12345@moonpoint.com>... Mail from 65.54.186.64 refused - see http://www.dnsbl.us.sorbs.net/

   Look for the "Status" and "Diagnostic-Code" values to determine why the message was rejected. In this case, the message was rejected because it is on the SORBS blacklist.

   If the IP address of the system attempting to send the email is listed in the SORBS blocklist, then the mesage is rejected with the message Mail from xx.xx.xx.xx refused - see http://www.dnsbl.us.sorbs.net/ with xx.xx.xx.xx being the IP address of the sending system. Note that it is up to the administrator of the receiving email server as to what text, if any, is included when the message is rejected. Many choose, like I do, to mention the blacklist that was used by the server to reject the message, but some may not provide any details as to why the message was rejected. So, if the status code is 5.7.1, but you don't see a reference to SORBS, it is still possible that email is being rejected from your Hotmail account by a server using the SORBS list, even though the rejection message doesn't actually mention SORBS.

5. Does this mean that I will not be able to receive email from any hotmail.com or msn.com email address?
   
   As a short-term solution, the email address of any hotmail.com or msn.com user with whom you correspond can be added to the system's "whitelist". Any email from an address on the whitelist will be accepted without going through any blacklist checks. As a long-term solution, software will be installed that will give blocked senders the option to override any blocks on the server themselves. Though, hopefully, Microsoft will also be addressing the problem with SORBS.

References:

1. Blacklists, Blocklists, DNSBL's, and survival: How to survive as a non-combatant in the Spam Wars
   By William K. Cole
2. Merits of RBLs?
   By Jim Pingle