What's Going On? -- SMTP Servers and Open Relays

Spam. It's all about spam, how it works, and how to stop it. Or at least slow it down a bit. We've made some changes at ACCC, designed to make it harder for spammers to send notes through our machines. Although this won't prevent you from receiving spam, we are now giving much less comfort to the enemy.

Most people will be unaffected, but those of you that connect from off-campus using an ISP could be affected, if your email program is not properly configured.

If you just want to cut to the quick, read this section. Otherwise read the background info below, and then come back here.

If you are connecting through an ISP (typically from home, but also if you travel to a conference with a laptop), you should not use the regular ACCC SMTP servers. Instead, use the ACCC's authenticated SMTP server mail.uic.edu or the SMTP servers provided by your ISP.

Step 1

Decide if you might be affected. Do you use an ISP for a home connection? Then you might be affected.

Step 2

Find out the name of your ISP's SMTP server. I happen to have a cable modem from MediaOne, so I use smtp.ce.mediaone.net. [Ha, Ha! MediaOne is long gone, isn't it?] Check out our incomplete list of SMTP server names. That might help, although you might have to contact your ISP and just ask. Or use the ACCC's mail.uic.edu, but setting it up is a lot harder.

Step 3

Configure your mailer to use the appropriate SMTP server. Eudora, Netscape, and Outlook are all different, of course. Check our instructions for Windows and our instructions for Macs or Using the mail.uic.edu Authenticated SMTP Server.

Step 4

Test it. Send yourself a note. Then relax.

What if you use multiple ISP's? If you move your laptop from home to campus to conference, or if you sometimes use the UIC Dialin servers, and sometimes a commercial ISP, then your best bet is to use the mail.uic.edu Authenticated SMTP Server.

Another answer is to use WebMail when you're "off-campus". WebMail runs on an on-campus machine, so it will always work, not matter how you're connected to the Internet.

You're at home and need to do some work. You boot your computer, connect to the Internet, fire up your mail program, compose a note, and hit Send. Think no more about it.

But what really happens when you send mail?

When you click send, your mailer checks its configuration for the address of an SMTP Server, typically a big computer run by your ISP. Then it connects to that SMTP server, sends the message, and disconnects.

An SMTP (Simple Mail Transport Protocol) server is basically the Internet mailman. The SMTP server will accept your message and find a way to deliver it. In rare cases it might deliver the message right away, but in most cases it will store the message on its disk, contact another SMTP server, and forward the mail on. Eventually, the note winds up at the destination, where it is stored in your recipient's Inbox.

SMTP is only used for sending mail. When you read mail, you probably use a protocol like POP or IMAP. The SMTP server you use has nothing to do with the POP server you use. They can, in fact, be miles apart on different networks.

Suppose you are in your campus office, and send a note to joe@caltech.edu. Your PC will contact an SMTP server at UIC and send the note. Similarly if you want to send a note to jane@harvard.edu, you again contact the SMTP server on the UIC campus. This is a fair use of our SMTP servers, because your PC is part of the UIC campus network.

If your friend Joe wants to send you a note, he would contact the SMTP server at CalTech. But actually you don't care -- it would be just fine if Joe directly connects to the UIC SMTP server. The note to mynetid@uic.edu would get handled by the UIC SMTP server as an incoming note, and gets sent to mailserv or tigger or perhaps some departmental machine. Again, this is a fair use of our SMTP servers because the note is destined for a campus mailbox.

But what if Joe sends a note to Jane? And what if Joe, at CalTech, makes a direct connection to a UIC SMTP server, with instructions to send the note to Jane, at Harvard? This is an open relay situation, and is not a fair use of the UIC computers.

The more open relays a spammer can use, the harder he is to trace. Spammers like to send notes, but they don't like to get caught or blocked. The more anonymous they are while sending mail, the harder it is to stop them.

The best way to close an open relay is to check the sender machine and the intended recipient.

• If the sending machine is on-campus, let the mail go through.
• If the mail is being sent to an address of the form: netid@uic.edu then let the mail go through, even if the sender is from outside.
  (This is a slight change from the way this used to be. Before the ACCC SMTP servers would deliver messages to addresses of the form person@whatever.machine.uic.edu.)
• If the sending machine is off-campus, and if the receiving address is not of the form netid@uic.edu, then block the mail.

We have now closed the open relays in the ACCC SMTP servers, except for mail.uic.edu. If you happen to be using an ACCC SMTP server smtpservx.cc.uic.edu, even inadvertently, and your sending machine is off-campus, your mail to off-campus addresses and on-campus addresses to any machine other than uic.edu will be blocked.

We don't have to do that with mail.uic.edu, because to use it you have to present a netid and password, so we know you belong here. So it's always perfectly fine to send email for anyone who logs in to mail.uic.edu.

• If your machine is physically on campus and it is properly registered in the campus Domain Name Server, DNS, you are on the campus network. (For the rare exception, you know who you are. If your machine is not registered, it should be. You can't use UIC Human Resources's Nessie system, either, from a machine that is not registered. See your department's Reach representative to get your machine registered.)
• If you dial up to the UIC dialin lines, you are on the campus network.
• If you use WebMail, you are on the campus network.
• If you connect through an ISP, such as MediaOne, AOL, NetZero, or any of the other 10,000 companies, you are off campus. That's not bad, but it does mean you should not use the regular ACCC SMTP servers for outgoing mail! Use either mail.uic.edu or your ISP's SMTP server.