Microcomputer Services

E-mail Relay Block (SMTP)

Overview
The University of Oregon Computing Center blocks the relay of external e-mail in response to an ever-increasing junk mail problem, effective November 24, 1997. The process of blocking outgoing mail is called an SMTP relay block.

Background
SMTP (Simple Mail Transfer Protocol) is the Internet protocol for sending e-mail. It is purposefully simple, which makes it easy to use and troubleshoot. Unfortunately, this simple design can be easily exploited so that e-mail sent from one party can appear to be from another. This particular exploit is useful for unscrupulous junk e-mailers. Until November, 1997, our timesharing hosts could be made to act as a relay for large amounts of junk e-mail without our permission or knowledge. One reason this is bad is that the junk e-mail appears to be sent from the University of Oregon. This means that the receiver's reply (or likely complaint) comes to us instead of the real offender. Turning off SMTP relay for external sites, while certainly not a catch-all solution, is a big step toward thwarting this type of attack.

Who Is Affected?
If you connect to an Internet Service Provider (ISP) other than UO, you will be affected. Users who connect to UO's network via modem, ethernet or wireless will not be affected.

There is one exception to this rule: those who use UO's webmail to send and receive mail. UO Webmail users will be unaffected, regardless of who is used as an ISP.

Technical Explanation
If your internet connection receives a UO IP address (one that begins with 128.223), you can use our SMTP servers. Otherwise, you must use the SMTP server provided by your ISP.

How To Work Around the SMTP Block
There are several ways to work around the SMTP relay block:

More Information
For more information on spam and anti-spam techniques, visit the following web sites:

http://www.sendmail.org/antispam.html
Anti-spam information from the canonical sendmail source.

http://spam.abuse.net/spam/
An excellent all around resource on the problem of spam.

http://maps.vix.com/rbl/rationale.html
An explanation of the Vixie Realtime Blackhole List/Mail Abuse Protection System, with an explanation of how and why spammers use SMTP relay; reading this reference will help you understand why we want to be good network neighbors when it comes to avoiding spam via SMTP relay.

More Help
Issues relating to our timesharing hosts (Darkwing, Gladstone) and using Pine can be best addressed by Academic User Services at 346-1758.

Other questions can be answered by Microservice's Help Desk.