Can you add customers to your email list without asking them first?

Ascent Vision · Published October 25, 2026

Ask first. Permission is not among the main requirements in the FTC's CAN-SPAM guide, which asks for an honest sender and subject line, a clear label that the email is an ad, a valid postal address and an opt-out honored within 10 business days. But Google's sender guidelines tell senders to make sure recipients opt in, and say people who did not sign up might mark your messages as spam. This is a plain summary, not legal advice.

What the FTC's guide lists

The Federal Trade Commission's CAN-SPAM compliance guide says the law covers all commercial email, including a message to former customers. Its main requirements include accurate header information, an honest subject line, a clear disclosure that the message is an ad, your valid physical postal address and a clear way to opt out. It says opt-out requests must be honored within 10 business days. The related answer on email marketing lists the main requirements.

Getting permission before the first email is not among the main requirements the guide lists. In its note on subscription and membership programs, it says "you don’t need to get members’ consent to send them marketing emails", and that members can still opt out. That is the FTC's description of the federal law; it does not settle state rules or other laws. This is a plain summary, not legal advice.

Receipts and appointment emails are different

The guide says a message with only transactional or relationship content, such as one confirming a purchase the customer already agreed to, is exempt from most of the law's provisions, though it still may not contain false or misleading routing information. It says the law views those categories narrowly. When one email mixes the two, the guide says it counts as commercial if the subject line would lead the reader to think it is an ad, or if the transactional part does not appear mainly at the beginning.

Google's sender guidelines add a mailbox provider's view: do not mix different types of content in one message, for example promotions in sales receipt messages. As general advice, keep the appointment email about the appointment, and send offers separately to people who said yes.

Why asking first still matters

Google's guidelines for sending to personal Gmail accounts say to make sure recipients opt in, and warn that people who did not sign up might mark your messages as spam. These are a mailbox provider's rules, not a law; the related answer on buying an email list covers what they mean for the email you send to customers who did ask.

A simple opt-in at booking

The easiest moment to ask is when someone books: one unchecked line on the booking form or estimate sheet asking whether they would like occasional emails, saying what they will get and how often. Then send only that, with a working unsubscribe link in every marketing email. The related answer on buying an email list has more ways to grow a list.

Sources

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