Why can people not send me email?

In most cases where people are have problems sending you email the senders email server is configured incorrectly, and it can serve as a security risk to everyone on the internet.  We at Internet Partners are willing to work with the administrators of these servers to help solve this problem. 

An open mail relay used to be a good idea

By not putting any security on this feature, you were helping e-mail distribution. But then along came the explosive growth of the Internet. In no more than a year, open relays went from being helpful to being security holes.

Even now, some people want to leave relays open to make it easier for remote users, who are using Dynamic Host Con figuration Protocol or the like, to get a pseudorandom IP address. That's not a good enough reason. There are other solutions, such as virtual private networks, that can get people their mail without opening your mail server to the world.

That is because an open relay not only lets people send unwelcome mail through your mail server, but it also can help make it impossible for someone who's being sent this mail to find out who really sent it.

RFC 2505
In February 1999, the IETF released RFC 2505, "Anti-Spam Recommendations for SMTP MTAs." This RFC explains the problems associated with unsolicited commercial email (UCE, or spam) and specifies the functionality that an SMTP Message Transfer Agent (MTA) needs to reduce UCE's effects. RFC 2505 makes 13 recommendations, two of which are most closely related to relaying:

FBI/CERT Security Checklist

ENSURE mail is configured to deny relaying from unknown hosts. This helps to prevent your mail server from being used inappropriately. Internet Partners mailserver mail.ipinc.net is configured to deny relaying from unknown hosts.

What is an open mail relay?

An open mail relay occurs when a mail server processes a mail message where neither the sender nor the recipient is a local user. In this example, both the sender and the recipient are outside local domain. The mail server is an entirely unrelated third party to this transaction. The message really has no business passing through this server.

How ORDB works  

ORDB.ORG is one of the two databases that Internet Partners uses to check the mail that is sent to our server.  The other is ORBZ.ORG.

Legend
* Sender of the mail
** Senders outgoing mailserver
*** mail.ipinc.net  incoming mailserver
**** ORDBs server

  1. Sender delivers  mail to an outgoing mailserver. A so-called SMTP-server.
  2. Senders outgoing mailserver establishes a connection to Internet Partners  mailserver [mail.ipinc.net], and attempts to deliver email to the recipient.
  3. Internet Partners mailserver queries the ORDB database, to see if your outgoing mailserver is listed as an open relay.
  4. The ORDB server responds to the Internet Partners mailserver, and tells it whether the senders outgoing mailserver is listed.
  5. If the senders outgoing mailserver turns out to be listed as an open relay, Internet Partners mailserver will choose to reject the connection from your mailserver and tell it that it is not allowed to deliver your mail. The sender will receive a so-called "bounce" or a "Mailer Daemon", telling them that their email could not be delivered.

NOTE:  The sender should then contact the administrator of their outgoing mailserver with this information to help close the open relay.  We at Internet Partners are willing to work with the administrators of these servers to help solve this problem. 

Why do open relays represent a problem?

The legitimate use of mail relay are dwarfed by the number of mailer hijackings. A hijacking occurs when massive amounts of mail are relayed through a server. Most hijackings are done by junk emailers -- the so-called spammers -- trying to spew their unwanted messages all over the Internet.

In the past mail relay was a useful tool. These days, thanks to the spammers, mail relay is a significant threat to Internet operations, and security.  A spammer can send out a message that can be more than just junk.  The Nimda virus attack is an example of something that could be first spread through an open email relay.  

How is the problem fixed?

Here are some pointers on how to secure your current mail system against third-party relay. Locate your mailer in the table below, and jump to the suggestions on what to do. (click here for details)  

 

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