CAN-SPAM and your email signature: what the US rules actually require

The CAN-SPAM email signature question has a short answer. The US law covers commercial messages, meaning email whose primary purpose is advertising or promoting a commercial product or service, and the FTC’s compliance guide says there is no exception for business-to-business email. The guide does not mention email signatures or one-to-one correspondence at all. So the safe reading is: a normal reply from a colleague is not what the definition describes, a marketing email is, and a promotional banner in a signature is a question for your lawyer. This is general information, not legal advice.

We read the FTC’s CAN-SPAM Act: A Compliance Guide for Business on 4 October 2026. The page is dated August 2023, with a note that it was edited in January 2024 to reflect inflation-adjusted civil penalty maximums. We quote it and say where it is silent. We also opened the FTC’s CAN-SPAM Rule page, which describes rules on how to determine a message’s primary purpose and cites 16 CFR Part 316, but we did not read the rule text or the Act itself. Rely on this page for what the FTC guide says, not for the full law.

What the CAN-SPAM email signature question covers

The guide says: “Despite its name, the CAN-SPAM Act doesn’t apply just to bulk email.” It covers all commercial messages, which the law defines as “any electronic mail message the primary purpose of which is the commercial advertisement or promotion of a commercial product or service”, including email that promotes content on commercial websites. It adds: “The law makes no exception for business-to-business email.”

For deciding whether a message is covered, the guide says what matters is the “primary purpose”. It describes three kinds of content an email can have: commercial content, which advertises or promotes a commercial product or service; transactional or relationship content, which facilitates an already agreed transaction or updates a customer about one; and other content, which is neither. A message with only commercial content must comply. A message with only transactional or relationship content “may not contain false or misleading routing information, but is otherwise exempt from most provisions”.

It also covers messages that mix the two. If a recipient reading the subject line would likely conclude the message contains an advertisement, or if the transactional content does not appear mainly at the beginning, the primary purpose is commercial.

What the guide does not say about a CAN-SPAM email signature

Email signatures are absent from the guide, and so is ordinary one-to-one business correspondence. Everything below about a CAN-SPAM email signature is our reading, not the FTC’s. Our reading is limited:

• If your staff send ordinary replies and the content is not an advertisement or promotion, the definition quoted above does not describe those messages.
• If your signature carries a promotional banner, such as “Book a demo this month”, the guide gives no answer. It is a question for a US lawyer: does the banner change the message’s primary purpose?
• If your marketing team sends campaigns, those are commercial messages, and the requirements apply to them.

That is why we recommend a factual CAN-SPAM email signature for staff, and putting campaign material in marketing emails, where the rules are clear.

The requirements, mapped to a CAN-SPAM email signature or footer

The FTC lists the main requirements. Here is each one and where it lives.

FTC requirement (guide’s wording)	Where it lives	Is it a signature line?
Don’t use false or misleading header information: “From,” “To,” “Reply-To,” routing information must be accurate and identify the person or business who initiated the message	Mail system settings and sender names	No
Don’t use deceptive subject lines	Subject line	No
Identify the message as an ad, “clearly and conspicuously”	Message body or footer	Possibly, as a line in the message
Tell recipients where you’re located: a valid physical postal address	Footer	Yes, a footer line
Tell recipients how to opt out, with a clear and conspicuous explanation	Footer	Yes, a footer line
Honor opt-out requests promptly: within 10 business days	Your process, not text	No
Monitor what others do on your behalf	Your process	No

Four notes from the guide on the lines that belong in a footer.

The address. According to the FTC, the message “must include your valid physical postal address”, and that this “can be your current street address, a post office box you’ve registered with the U.S. Postal Service, or a private mailbox you’ve registered with a commercial mail receiving agency established under Postal Service regulations”. If you do not want to publish an office address, that wording lists the alternatives it accepts.

The opt-out explanation. It must be a clear and conspicuous explanation of how to opt out of future marketing email. The guide says to craft the notice so an ordinary person can recognise, read and understand it, and suggests creative use of type size, colour and location can improve clarity. It says to give a return email address or another easy internet-based way to communicate the choice.

The opt-out process. The FTC says any opt-out mechanism must be able to process requests for at least 30 days after you send the message, that you must honour a request within 10 business days, and that you cannot charge a fee, require more than an email address, or make the recipient take any step other than sending a reply email or visiting a single page on a website.

Responsibility. Even if you hire another company to handle your email marketing, the FTC says you cannot contract away your legal responsibility, and that both the company whose product is promoted and the company that sends the message may be held responsible.

A CAN-SPAM email signature footer for marketing messages

Here is an example footer for a campaign email. The company and address are made up, and this is a drafting example to discuss with a lawyer, not guaranteed-valid wording.

You are receiving this because you asked to hear from Harbour Studio. Harbour Studio, 500 Market Street, San Francisco, CA. To stop receiving marketing email from us, reply with the word STOP or visit [unsubscribe link].

This belongs in the footer of marketing messages, not in each staff member’s signature. A staff signature drawn by emailfooter, with a street address but no promotion, looks like this:

A profile layout with a street address and no promotion. The company and person are made up.

If you want the address in every staff signature as a matter of branding, our page on the address in an email signature covers the practical side.

The penalty, and why to check it

The FTC says each separate email in violation of the CAN-SPAM Act is subject to penalties of up to $53,088. The note on the page says that figure was edited in January 2024 to reflect inflation adjustments, so check the FTC’s current figure before quoting it. The page also says the Act has aggravated violations and criminal penalties for certain conduct, such as using false information to register multiple email accounts.

Where this stops: other countries

CAN-SPAM is a US law. Canada, the UK and other places have their own rules for commercial email, with different tests and sometimes stricter ones. We have pages on CASL and email signatures and on PECR and business email marketing, and those pages state what we read for each. Nothing in the FTC guide tells you how another country treats your email.

What this means for a team’s CAN-SPAM email signature

1. Decide what the CAN-SPAM email signature is for. Name, title, company, phone and address are factual. A “book now” banner is promotion.
2. Keep campaigns in campaign tools. Your email marketing platform should add the address and opt-out lines. Check it does.
3. Ask a lawyer about banners in staff signatures. The guide does not address them.
4. Write one rule. Put it in your brand guidelines and your company signature plan, including who may add a banner and who approves it.
5. Do not rely on a disclaimer. The email disclaimer examples are for discussion with a lawyer. The guide does not say a disclaimer changes what CAN-SPAM requires.

A tool such as emailfooter is for staff signature blocks. It has no unsubscribe features and does not send campaigns, so it is not a replacement for your marketing platform.

Frequently asked questions

Does CAN-SPAM apply to B2B email?

The FTC’s guide says “The law makes no exception for business-to-business email.” What counts is whether the message’s primary purpose is commercial advertisement or promotion.

Does a CAN-SPAM email signature rule apply to a normal one-to-one business email?

One-to-one correspondence is not discussed. The definition it quotes covers messages whose primary purpose is advertising or promoting a commercial product or service. Ask a lawyer about borderline cases.

Do I need a physical address in my CAN-SPAM email signature?

For commercial messages, the guide says the message must include a valid physical postal address. It does not say ordinary staff signatures need one. Put it in your marketing footer.

Does CAN-SPAM require an unsubscribe link in every email?

Per the FTC, commercial messages must include a clear explanation of how to opt out, through a reply address or another easy internet-based method. Transactional or relationship messages are, in its words, “otherwise exempt from most provisions”.

What is the CAN-SPAM penalty?

Up to $53,088 per violating email, in the figure edited in January 2024. Check the FTC’s current figure.