Comprehensive Anti-Spam Services

ITS offers a suite of anti-spam services that work together to provide a comprehensive approach to fighting spam. Individual services are described below the diagram.

Diagram showing ITS's anti-spam services.

PenaltyBox
Postmaster Blocks
Three Strikes
Do Not Spam List

Members-Only and Moderated Groups
SpamBox
Your Program's Anti-Spam Feature
Glossary

PenaltyBox

PenaltyBox checks mail from external IPs (mail coming from umich.edu IP addresses is exempted) that is sent to @umich.edu addresses for the following characteristics:

Compliance with Internet and e-mail system best practices and protocols.
Whether the connecting IP is included on the Do Not Spam List.

PenaltyBox then causes a temporary delivery failure to be generated for mail it considers questionable. PenaltyBox stores information about the mail, and if delivery is retried, the mail is accepted for delivery.

Postmaster Blocks

The Postmaster Group handles e-mail delivery problems, responds to questions sent to postmaster@umich.edu, and deals with other e-mail related issues. The Postmaster can institute blocks as needed when there are problems that impact mail delivery for the U-M community.

Three Strikes

Spammers often send mail to lists of randomly generated adresses in the hopes of some of those addresses turning out to be real. If an IP address attempts to send mail to too many unknown users (addresses for people who do not exist), it is likely that the IP address is being used to send spam. Generating a temp failure (like PenaltyBox does) for this mail stops the spam but lets any legitimate mail through after a delay of just a few minutes.

Do Not Spam List

This service uses published lists from vendors to identify mail sent by known spam sources and blocks the mail so that it is not accepted for delivery. You can turn use of the Do Not Spam List on or off for your own @umich.edu address and the addresses of groups that you own in the U-M Online Directory. (See instructions.)

Members-Only and Moderated Groups

If you own a group in the U-M Online Directory, you can set it up in ways that will reduce the amount of spam received by members of the group.

Members-Only Groups are groups where only mail sent by members of the group is delivered to the group members. In other words, you must be a member of the group in order to send mail to it. Spammers can't get through at all.
Moderated Groups are groups where a moderator screens all mail sent to the group and passes on only the mail that is appropriate. While this makes things easier for the group members, it is extra work for the person who is designated to be the moderator.

SpamBox

SpamBox is a filter that puts suspected spam messages in a SpamBox folder, where you can do a quick check for any messages you might want to keep before deleting the spam. Use SpamBox to keep the spam messages that get past the Do Not Spam List and the spam blocks at the U-M Mail Gateway from cluttering your INBOX. You must sign up for SpamBox to use it; there is no charge. (See instructions.)

Your Program's Anti-Spam Feature

Your mail program may include its own anti-spam tool. Check the documentation for your mail program for details.

Glossary

Brightmail: A commercial anti-spam product. The ITS Exchange E-Mail Service uses Brightmail to reduce spam.
directory transactions: When mail sent to an address ending in "@umich.edu" reaches the mail gateway machines, the mail gateway machines essentially look up the appropriate uniqname or groupname in the directory to find out where to deliver the mail.
ITS IMAP e-mail service: This service is automatically available—at no cost—to students, faculty, and regular staff. It's a part of the University's standard computing services.
ITS Exchange e-mail service: This service is a charged-for service available only to faculty and staff in participating departments.
postmaster: The Postmaster Group handles e-mail delivery problems, responds to questions sent to postmaster@umich.edu, and deals with other e-mail related issues.
SMTP transaction: "SMTP" stands for Simple Mail Transfer Protocol. It is a protocol used for sending e-mail messages between servers. The SMTP transaction is basically the conversation that takes place between a mail-sending machine and a mail-receiving machine regarding delivery of a mail message. For an example, see the annotated SMTP transaction provided by slett.net.
temp failure/temporary delivery failure: Mail-receiving servers generate temp failures routinely for a number of different reasons—temporary hardware or software failures, users over quota, transient network problems, and more. The standard response from mail service providers is to queue temp-failed mail and try to resend it later, typically within 5-60 minutes.
U-M mail gateway: A group of machines that receive mail sent to addresses ending in "@umich.edu."