USC's Information Services Division (ISD) recently disabled "mail relaying" from non-USC hosts on the main USC relaying system, relay.usc.edu. This has caused some problems for people who use a non-USC Internet Service Provider (ISP) and have their e-mail configuration set to use relay.usc.edu as the relaying system.
A mail relaying system (also known as an SMTP server) is one that accepts mail from one host, such as your PC or Mac, and relays it to another host. In "the old days" before the growth of the Internet nearly all systems did mail relaying primarily because there was little reason not to. Unfortunately systems that do relaying are often exploited by people who wish to send out huge volumes of e-mail, known as "spammers". A spammer can send a single message to a relaying sytem and let it do the work of sending out thousands of copies of the message to other recipients on the network. The spammer can usually hide his presence and the system that does the relaying, such as relay.usc.edu, gets the blame for all the e-mail that was generated. To stop this, most sites disable relaying in their mail handling software entirely, or enable it only for use from a specific group of systems. For example, imsc.usc.edu and sipi.usc.edu will do relaying only for systems in the usc.edu domain. Other Unix systems in IMSC and SIPI will not do relaying at all.
Over the past few months ISD has been running checks on most of the systems on campus to see if they were doing mail relaying. In most cases the systems had been configured some time ago and the owners didn't know they were relaying. The goal was to get all systems on campus to refuse relaying from outside USC. This does nothing to help the problem of spamming that originates from within the USC network. That problem can presumably can be addressed by other means.
On April 2nd (and without much warning), ISD configured relay.usc.edu to no longer relay messages from non-USC hosts. This change in relay.usc.edu has caused problems for USC people who use an other ISP, such as AOL, Earthlink or Pacbell, to connect to the Internet from home or when travelling. Many of these people had specified relay.usc.edu as the relay host even though they were connected to the Internet through some other ISP. As long as relay.usc.edu did relaying this worked fine. However when the relaying was shut off, their mail could not be delivered.
None of the changes that ISD has made should affect a USC user if they have their system configured properly. All ISP's run a mail relaying system that is intended to handle the relaying of mail for their users. If you dial in directly to USC over a PPP connection, then you are using USC as the ISP and can use relay.usc.edu for relaying. If you connect to another ISP, such as Earthlink, then you should be using Earthlink's relaying system to send mail. Even when relaying through USC was allowed, there was no advantage to using relay.usc.edu for mail relaying as opposed to using the ISP's system.
Below is a list of some of the more popular ISPs and the name of the system that should be doing the relaying for users of that ISP. In the set-up parameters for the mail software on PCs and Macs, the relaying host is usually referred to as the SMTP host.
| ISP | SMTP host | |
| Earthlink | mail.earthlink.net | |
| Pacbell | mail.pacbell.net |
In Netscape 4.7, under the Edit menu select "Preferences". In the Preferences dialog select "Mail Servers" and insert the proper hostname where it says "Outgoing mail (SMTP) server".
In Eudora 4.2, under the Special menu select "Settings..." In the Settings dialog select "Hosts" and enter the information where it says "SMTP". Note that this is for the default or "dominant" personality. If you have created more than one personality for accessing various ISP's, the information needs to be entered in the "Personalities" settings where it says "SMTP Server."
Many people are confused about the difference between the system doing relaying of the mail and where replies to the message will go. There is no connection between the two. The reply-to address can be set in the mail program to whatever you want it to be. If the recipient of the message does a reply, it will go to that address regardless of what system relayed the mail to them. You do not have to use a USC relaying system in order for people to send a reply back to your USC e-mail address.
In Netscape 4.7, the reply-to address is set in the "Identity" preferences. In Eudora 4.2, the reply-to address is set in the "Getting Started" settings for the dominant personality and in the "Personalities" settings for other personalities.