How can I stop junk email?

People sending electronic "junk mail" generally use a fake "From" address to avoid receiving millions of responses complaining about their abuse of the Internet and to make it more difficult for people to complain to their Internet Service Provider. In addition a fake "To" address may be added to appear to be at the recipient's site or to make the message look more 'normal', since many people ignore mail from unknown sites in an effort to avoid junk mail. Usually, a brief examination of the headers will indicate that the "@seas" address is fake.

Spamblock:

Installed on Eniac is a system that can filter out junk mail based on a set of "junk mail criteria" and a list of known spam-sources provided by the user. For more information, please visit the Answers page on the subject:

http://www.seas.upenn.edu/cets/answers/spamblock.html

Using an Anonymous Address:

If you want to alter your return address for anonymity or to avoid "junk mail", alter the username part, not the hostname part.  Eniac will now reject any mail that claims it is from a non-existent host.

For example,

chip.nospam@seas.upenn.edu

will work, but

chip@nospam.seas.upenn.edu

will be rejected.

Our system attempts to do a DNS ("Domain Name System") look up of the hostname part of the return address, and if the host is not listed the message is rejected. The username part of the return address does not have to exist.

We do not block email based on content, source, or destination. However, there are technical reasons for rejecting mail that has an invalid host in the return address.

If we accept a message with an invalid host in the return address, and it is undeliverable, our mail server must spend an inordinate (and unnecessary) amount of time in attempting to return the unreturnable mail. It keeps on trying in case the name server is having a temporary problem. Once this wasted time is spent, the mail has to be handled by our staff, which wastes their time.

With junk mailers attempting to avoid the responses that their advertisements provoke, and many other people trying to avoid getting on spam mailing lists, fictitious return addresses have become common in electronic mail. The problem with bad return addresses used to be a very minor annoyance, but it has grown to the point where we had to take action to eliminate it. Most of the messages that will now be rejected are Internet junk mail.

Additional anti-spam resources at Penn

Stopping junk mail from reaching your account is very difficult. However, after you get it, you can try to do something about it. Information about spam (and responses to it) is available in http://www.upenn.edu/computing/security/advisories/spam.html, including how to complain to their postmaster.

If the email is actually sent from Penn. complaints to the postmaster (of the sending machine) are likely to have an effect, particularly if the mailing is a pyramid scheme or commercial solicitation. Be sure to include the complete email headers. If the mail is sent from outside Penn, it varies.