What an unsubscribe link has to do

The short answer

A commercial email message has to contain a functioning return electronic mail address or other internet-based mechanism, clearly and conspicuously displayed, that a recipient may use to request not to receive future commercial email from that sender at the address where the message was received.

That mechanism has to remain capable of receiving such requests for no less than thirty days after the original message was transmitted.

Once a request is made, it is unlawful for the sender to initiate a commercial message falling within the scope of the request more than ten business days after receiving it.

And a Federal Trade Commission rule sets a ceiling on what may be asked in exchange. Neither a sender nor anyone acting on a sender's behalf may require a recipient to pay any fee, provide any information other than the recipient's email address and opt-out preferences, or take any step except sending a reply email or visiting a single internet web page, in order to use the mechanism or to have the request honoured.

The single-page ceiling is the operative limit

That last requirement is the one worth reading twice, because it describes the friction most people have actually encountered.

A single internet web page is the maximum. A flow that asks a reader to sign in, then find a preferences area, then confirm on a second screen, is a sequence the rule addresses directly.

The information ceiling is equally specific. The only things a sender may require are the email address and the opt-out preferences. A form asking for a name, a reason for leaving, an account number or a phone number is asking for information beyond what the rule permits it to require.

The fee prohibition is absolute in its own terms and does not have an exception written next to it.

The statute does permit a sender to offer more granularity, but only in one direction. A sender may comply by providing a list or menu from which the recipient chooses which types of commercial email to receive or not receive, if the list or menu includes an option under which the recipient may choose not to receive any commercial email from that sender. A preference centre with no unsubscribe-from-everything option is not what that provision describes.

What counts as a commercial message, and what does not

None of the above applies unless a message is commercial, and the rule sets out how that is decided rather than leaving it to intuition.

If a message consists exclusively of the commercial advertisement or promotion of a commercial product or service, its primary purpose is deemed commercial. That is the easy case.

The mixed cases are where the rule does its work. If a message contains both commercial content and transactional or relationship content, its primary purpose is deemed commercial if either a recipient reasonably interpreting the subject line would likely conclude that the message contains a commercial advertisement or promotion, or the transactional or relationship content does not appear, in whole or in substantial part, at the beginning of the body of the message.

A third rule covers messages mixing commercial content with other content that is neither transactional nor relationship. There the test is the subject line, or whether a recipient reasonably interpreting the body would likely conclude the primary purpose is commercial. The rule names factors illustrative of that interpretation: the placement of the commercial content, in whole or in substantial part, at the beginning of the body; the proportion of the message dedicated to it; and how colour, graphics, type size and style are used to highlight it.

A message is deemed transactional or relationship only if it consists exclusively of transactional or relationship content.

The five categories that are not marketing

The rule lists what transactional or relationship content is, and the list is closed.

Content to facilitate, complete, or confirm a commercial transaction the recipient has previously agreed to enter into with the sender. Content providing warranty information, product recall information, or safety or security information about a product or service used or purchased by the recipient.

Content relating to a subscription, membership, account, loan, or comparable ongoing commercial relationship involving the recipient's ongoing purchase or use of the sender's products or services, to provide notification of a change in the terms or features, notification of a change in the recipient's standing or status, or, at regular periodic intervals, account balance information or another type of account statement.

Content directly related to an employment relationship or a related benefit plan the recipient is currently involved in, participating in, or enrolled in. And content delivering goods or services, including product updates or upgrades, that the recipient is entitled to receive under the terms of a previously agreed transaction.

Two implications follow for anyone reading their own inbox. A shipping notice, a renewal-terms notice and a recall notice sit inside these categories on their face. And a message that pairs one of those with a promotion does not stay in the category, because the deeming rule requires the message to consist exclusively of that content.

Who the sender is when several companies are promoted at once

One definitional paragraph handles a structure that is common in referral and affiliate arrangements, and it is the reason a single email can have more than one company standing behind it.

When more than one person's products, services, or internet website are advertised or promoted in a single email message, each such person within the statutory definition of sender is deemed to be a sender.

The rule then provides one route to a single sender. Only one person will be deemed the sender if that person is within the statutory definition, is identified in the from line as the sole sender of the message, and is in compliance with a named list of statutory provisions and with the rule's own opt-out ceiling.

The practical consequence is that the from line is doing legal work. A message promoting several companies with one name in the from line is making a claim about who is answerable for it, and the rule conditions that claim on compliance rather than on the styling of the header.

The address at the bottom, and what it has to be

Every commercial email has to provide three things: clear and conspicuous identification that the message is an advertisement or solicitation, clear and conspicuous notice of the opportunity to decline further commercial messages from the sender, and a valid physical postal address of the sender.

The rule defines that last term rather than leaving it open. A valid physical postal address means the sender's current street address, a Post Office box the sender has accurately registered with the United States Postal Service, or a private mailbox the sender has accurately registered with a commercial mail receiving agency established pursuant to Postal Service regulations.

Each of the three permitted forms carries the word current or accurately registered. The definition is about a mailbox that exists and is registered, not about a string of text that looks like an address.

There is also a provision about what happens to an address after someone opts out. Once a request has been made, it is unlawful for the sender, or any other person who knows the request was made, to sell, lease, exchange, or otherwise transfer or release the recipient's email address, including through any transfer involving mailing lists bearing that address, for any purpose other than compliance with the statute or another provision of law.

That is the provision most relevant to a market where contact details are collected at an intake and the same address later appears on unrelated mail. It is a restriction on transferring the address, not merely on sending to it.

Sources

Each document below is named as it names itself, with the date printed on that document rather than the day it was read.

1. Title 16 Code of Federal Regulations Part 316, Can-SPAM Rule, read in full — the definitions at 316.2 including the multiple-sender proviso at (m) and valid physical postal address at (p); the primary purpose criteria and the five categories of transactional or relationship content at 316.3 with its footnote; and the prohibition on charging a fee or imposing other requirements on recipients who wish to opt out at 316.5; Source note 73 FR 29677, May 21, 2008 — Electronic Code of Federal Regulations, Office of the Federal Register, September 2026
2. United States Code Title 15, Section 7704, Other protections for users of commercial electronic mail — read at subsection (a)(3) for the return address mechanism, the thirty-day availability requirement and the list-or-menu option; (a)(4) for the ten business day objection deadline and the prohibition on transferring an address after a request; and (a)(5) for the advertisement identification, opt-out notice and valid physical postal address requirements — Office of the Law Revision Counsel, U.S. House of Representatives, September 2026