Unsolicited Bulk Email: Definitions and Problems

prepared by
Paul Hoffman
Internet Mail Consortium

Internet Mail Consortium Report: UBE-DEF
IMCR-004, October 5, 1997

Unsolicited Bulk Email (UBE) has become a major concern for Internet users due to the increasing amount of UBE that typical Internet users receive. Many proposals for technical and legislative remedies are being suggested, but few proposals define UBE or list its negative effects. This paper sets forth standard definitions and gives an overview of UBE effects, without proposing or supporting particular mechanisms for controlling their occurrence.



Unsolicited Bulk Email, or UBE, is Internet mail ("email") that is sent to a group of recipients who have not requested it. A mail recipient may have at one time asked a sender for bulk email, but then later asked that sender not to send any more email or otherwise not have indicated a desire for such additional mail; hence any bulk email sent after that request was received is also UBE.

A common term for UBE is "spam", although that term encompasses a wider range of intrusive transmissions. For instance, the term "spam" originated in the realm of Usenet news, not email. There, individuals cannot request or refuse bulk email, although some newsgroups explicitly permit or encourage its inclusion as a part of the group charter.

Note: the first version of this report used the term Unsolicited Commercial Email (UCE). That term was originally chosen because much of the early debate about UBE was centered in the United States where commercial speech can be regulated by the government but political and religious speech cannot. However, on reflection, because UBE is an international problem, the term "UCE" was changed in this report to "UBE". Limitations on the control of UBE, such as having to have different laws for political UBE versus commercial UBE, will be a local matter.

Destination Operator

Internet Email is processed by origination, relay and destination system (host) operators, primarily transmitting messages with the SMTP mail standard. An Origination Operator is an organization or individual that is responsible for the host which places a new piece of email into the Internet. A Relay Operator mediates email transmission between origination and destination systems. A Destination Operator is an organization or individual that maintains or controls a service for recipients of email and for allowing recipients to access their mail using a mail user agent. Destination Operators may also provide relay services and almost always provide origination service for the same users who are recipients.

These specialized terms are used here instead of the single, more common "Internet Service Provider" (ISP) because tens of millions of people get their mail service from organizations that are not ISPs. Almost everyone who gets email at their desk at work use their employers as a Destination Operator, but those companies are not ISPs. Also, many people get their Internet mail through free accounts in public libraries, schools, and so on, and the organizations running those mail servers should be differentiated from ISPs because they often are offering email access as a public service.

In many cases, ISPs which provide basic connectivity have no direct part in the problems associated with UBE. On the other hand, all Internet mail operators must deal with UBE problems every day. Hence, the terms introduced here include organizations providing Internet mail service to employees, as well as libraries and schools providing free service for their "customers" and also includes ISPs that include email within their set of products.


A recipient is a person who receives email. (Programs can also receive email, but they do so on behalf of a person.) Most recipients usually receive email from two kinds of senders: other people, and Mailing List Agents. Some email addresses refer to a "role" within the organization (such as "sales" or "postmaster") and might have multiple people processing email sent to it, or might have a software program respond automatically. In either case, UBE must still be handled by the recipient.

Mailing List Agent

A Mailing List Agent (MLA) is a software program that acts like a recipient, but does special processing upon receiving email: it resends the email to a list of recipients. Hence an MLA is a special form of email relay. Many MLAs are controlled by people, but some are completely automatic and involve no human intervention or decision-making.

MLAs are sometimes called "mailing lists" or "mailing list managers", although these terms do not define well the roles of the controlling software or of the people involved in controlling the software. Other terms, such as "listserv", are sometimes used generically but actually refer to specific implementations of MLAs.

Note that an MLA is not a recipient because it is not the final destination for the message, even though its email address might have been used for the UBE. Mail sent to an MLA will most likely be re-sent to many people, and those people are the recipients of the original mail, even though that mail has processed and re-sent by the MLA.

Problems Caused By UBE

Although the senders of UBE defend it as having little difference from traditional bulk mail, it in fact is quite different: UBE shifts almost all the costs of the message onto the recipients and their Destination Operators. The negative effects of UBE can be categorized into the effects on recipients, on the recipients' Destination Operators, and on the Internet backbone in general. Secondary effects also are felt by Origination Operators.

Further, many senders of bulk UBE use tactics which are often viewed as devious, and probably illegal, in order to reduce the cost to the sender or even to hide the true identity of the sender. Instead, costs are shifted from the actual sender to the receiver and their Destination operator. These tactics, which are becoming more common, are described separately because they are only tangentially related to UBE itself.

Effects On Recipients

End users are the ones who are most affected by UBE. The costs, to recipients, generally fall into two categories: real costs and social costs.

Real Costs To Recipients

UBE costs money to every recipient, as if it was sent "postage due". Probably the most important negative effect of UBE is the financial cost incurred transmitting it from the Destination Operator's host to the recipient user's host, such as through a modem. Many users have to pay their Internet access providers by the minute. Even users with fixed-cost Internet accounts often have to pay for the phone time to connect to their Internet access providers.

Multiply these costs by the hundreds of thousands or millions of users that many pieces of UBE go to, and you can see that the cost to recipients is quite high, even without taking into account the considerable costs to Destination Operators and the Internet backbone.

There are other costs paid by all UBE recipients that are similar to recipients of bulk postal mail. For instance, there is the time lost sorting UBE from wanted mail, the time lost opening unwanted UBE that is disguised as email that the user might want to read, and so on. As the quantity of UBE increases, the cost of doing this sorting can become quite significant. UBE is particularly an issue for companies where employees get email, since dealing with UBE is done on company time, thus causing lost productivity.

Social And Personal Costs

Widespread UBE has had a significant human cost as well. Many users know that posting to mailing lists or on Usenet news will likely cause them to receive UBE, so they no longer participate in what used to be the most vibrant communications medium on the Internet. The constant fear of irreversibly getting one's name on a mailing list has caused many people to avoid using them altogether.

Similarly, the act of having to sort through cleverly-worded UBE in order to find actual personal email has caused many people not to use email to its fullest potential. These types of effects are causing many new users to avoid checking their mail as often as they would otherwise like, again causing less use of what could be a valuable medium. Use of "filters" by a recipient's email software can reduce some of this pain, but cannot eliminate it. The current state of filtering technology cannot distinguish between legitimate, personal email and UBE.

Effects On Destination Operators

The costs of UBE go well beyond the recipient. Each Destination Operator pays for each email message received because a message takes up a certain amount of the Destination Operator's connectivity and computer bandwidth. Further, if the message is stored by the Destination Operator for a recipient, the operator must pay for the storage and the maintenance of that storage. Although the cost of a single UBE email to an individual recipient might well be quite small, the aggregate cost can be considerable.

Depending upon their specific business model, Destination Operators handle the costs of UBE differently. If the Destination Operator is an Internet Service Provider, the costs of UBE are borne by the ISP's users, through higher prices or lower service. If the Destination Operator is an employer, the costs of UBE are often taken out of the general networking budget, meaning that UBE causes lower company profits. If the Destination Operator is someone offering a free public mail service, UBE causes them to be able to offer less service to their clients.

Many Destination Operators report that they bear an additional and considerable expense, one of having to educate people about the nature of UBE and why they are receiving it. Because UBE tends to diminish people's desire to use the Internet, they are more likely to complain about it to their Destination Operators.

Effects On The Internet Backbone

UBE sent over the Internet backbone causes delays for all Internet users. Further, because most UBE senders use mailing lists that have outdated addresses on them, many messages are rejected ("bounced"), causing the intended Destination Operator to send a return response, which wastes more bandwidth.

Effects Caused By Malicious UBE Senders

Many of the complaints about UBE, by Destination Operators, stem from the common practice employed by UBE senders of misappropriating services. The methods of misappropriation, while technically easy to do, cause hundreds of thousands of dollars of damage to Destination Operators per year by shifting the burden of sending the UBE on Destination Operators who are unrelated to the UBE sender.

The typical way that a deceptive UBE sender misappropriates service is to offload return mail and complaint handling onto an unsuspecting Origination or Relay Operator by specifying one or more incorrect return addresses in the message itself. They route the UBE through an unrelated Origination Operator's SMTP service. Both of these actions are quite easy to do and can make the source of the message almost untraceable, particularly if the UBE sender is using a short-lived Internet account that was obtained for the purpose of sending this UBE. The account is used once, to do the sending, and is never accessed again. Hence, the sender need not care at all whether its use for this purpose is ascertained.

Beyond the basic cost of deceptive use, the result of the unwanted mailing often causes many complaints to be directed at the Destination Operator that should instead have been directed at the UBE sender. These complaints can cause significant damage to the Destination Operator, such as by filling up mailboxes on the mail hosts and reducing service to legitimate users of the Destination Operator.


Core problems associated with UBE stem from the very low cost on the sender and the real costs on the recipients and their Destination Operators. There is no other common form of unsolicited communication that shifts so much of the cost of each message onto the recipients. The costs are particularly high on novice users and the Destination Operators who have a preponderance of novice user clients, but the costs are in fact borne by all Internet users.

This IMC Report is IMCR-005 and is named UBE-DEF. The Internet Mail Consortium is an industry trade association for companies participating in the Internet mail market.