A polite way out, written into every cold email

If you send cold sales email from Gmail to people in the United States, you need to tell them how to stop hearing from you, even if you write one message at a time. It does not have to be an unsubscribe link. A plain sentence inviting a reply is enough for the law, provided you actually stop. What you do not need, below bulk volumes, is the one click unsubscribe header that Gmail asks of large senders. Most of the confusion comes from mixing those two rules up.

What US law asks of a single email

The FTC's CAN-SPAM compliance guide is direct about scope. The Act covers all commercial messages, meaning any email whose primary purpose is to advertise or promote a product or service, and the guide says it applies beyond bulk email and makes no exception for business to business mail. A personal note to one prospect about your product is a commercial message.

For each one, the guide asks for a clear explanation of how to opt out of future marketing email, written so an ordinary person would notice and understand it. It names the mechanism plainly: a return email address or another easy internet based method. The opt-out must keep working for at least 30 days after you send, and you must honour it within 10 business days. You may not charge a fee, ask for anything beyond an email address, or require more than a reply or a visit to a single web page. The same guide also requires a valid physical postal address in the message and a clear disclosure that it is an advertisement, and it puts the penalty at up to $53,088 for each email that breaks the rules.

For someone writing from Gmail, the practical version is a sentence above your signature, something like: If this is not relevant, reply and say so and I will not email you again. Add a postal address to the signature. Neither needs a tool.

Where Gmail's one click rule starts

Google's email sender guidelines set a separate, technical bar. Senders of more than 5,000 messages a day to personal Gmail accounts must support one click unsubscribe on marketing and subscribed messages, using the List-Unsubscribe and List-Unsubscribe-Post headers defined in RFC 8058. The sender guidelines FAQ adds that the 5,000 is counted across everything sent from the same primary domain, that a mailto or ordinary link in the body does not meet the requirement, that Google recommends honouring requests within 48 hours, and that these requirements do not cover mail sent to Google Workspace accounts.

So a salesperson sending 40 emails a day is outside that rule. Two lines in the same Google documents still apply to them. The guidelines tell every sender to give recipients an easy way to unsubscribe. And the FAQ, discussing what counts as promotional, says that message recipients, not Google, decide the nature of the messages they receive. Your cold email is promotional if the person reading it thinks so, and their alternative to an opt-out is the Report spam button. The FAQ notes that unwanted messages without an easy unsubscribe are more likely to be reported, and that a rising spam rate hurts delivery of everything else you send.

Writing to UK companies

The UK rules work differently. The ICO's guidance on electronic mail marketing lets you email corporate bodies such as companies and LLPs without prior consent, while sole traders and some partnerships count as individuals and need consent or an existing customer relationship. Every sender must give a valid contact address so recipients can opt out. For businesses, the ICO calls it good practice and good business sense to keep a do not email list of any company that objects, and to screen every new marketing list against it.

Where opt-outs actually fail

Few teams refuse an opt-out on purpose. The failures are operational. A sequence keeps running after the reply, or next month's imported list quietly adds the address back. Either one is a missed opt-out under the 10 business day rule, and each is the moment a polite prospect becomes a spam report.

• Write the opt-out in plain words, near the signature, where a reader looks for it.
• Treat any clear refusal as an opt-out, whatever the wording. Not interested counts as much as unsubscribe.
• Stop scheduled follow ups the same day you read the reply, not at the next weekly cleanup.
• Keep one do not email list for the whole company, and check every new list and every new sequence against it, as the ICO suggests.
• Ask for nothing in return. The FTC guide rules out fees, extra personal details and any step beyond a reply or a single page.

How Fast Mail Tracker handles it

Campaigns sent through Fast Mail Tracker carry a small unsubscribe link in the footer and the two RFC 8058 headers, so a mail app that supports one click unsubscribe can offer it. The link opens a confirmation page, and only the button on that page or a mail app's one click request records the opt-out, because security scanners open links on their own. One to one emails get no footer, by choice: an unsubscribe banner makes a personal note look like a newsletter. For those, write your own sentence.

Every address that unsubscribes, and every address that hard bounces, goes onto a suppression list for your workspace. That list is checked before each tracked email we deliver for you, campaign or one to one, so someone who opted out of a campaign does not receive your next personal follow up either. A skipped recipient shows as suppressed on that email rather than quietly appearing as sent. An opt-out that arrives as a reply still needs you to act on it, because the list records unsubscribes and bounces, not the wording of a reply.

This is a reading of the regulators' published guidance, not legal advice. Fast Mail Tracker is in early access while Google's security review completes, so places are limited; if you want opt-outs honoured across every send, the install button below is the place to start.