Can you email your whole list a Christmas offer?

Not the whole list, no. You can email anyone who specifically agreed to hear from you, anyone who has bought from you before and was given a clear chance to opt out, and any limited company. The prospects, the bought-in names and the sole traders who never agreed to anything are off limits, and at Christmas they're usually the biggest part of the list.

It's the second part of our series on Christmas marketing, checked. Like the rest, it sets out what the rules and the platforms say, with a link to each source, and it isn't legal advice.

Who you can email

The rule is regulation 22 of the Privacy and Electronic Communications Regulations, and the ICO sets it out in two parts. You mustn't send marketing email to an individual unless "they have specifically consented to electronic mail from you", or "they are an existing customer who bought (or negotiated to buy) a similar product or service from you in the past, and you gave them a simple way to opt out both when you first collected their details and in every message you have sent".

The second part is the one people lean on, but the ICO is blunt about its limits: it "does not apply to prospective customers or new contacts (eg from bought-in lists)".

Companies are treated differently

Under the same guidance, you can email "any corporate body (a company, Scottish partnership, limited liability partnership or government body)". The catch is who counts as one: "Sole traders and some partnerships are treated as individuals", so the plumber and the one-person consultancy need consent or the opt-out, while the limited company down the road doesn't. Even so, the ICO calls keeping a do-not-email list for firms that object "good practice, and good business sense".

The guidance may change

The ICO's own page carries a warning at the top: "Due to changes made by the Data (Use and Access) Act, this guidance is under review and may be subject to change." So the rules above are what the regulator says today, and they're worth checking again before you build a year's email plan on them.

Sorting the list before you send

• Split the list into four: people who specifically consented, past customers, limited companies, and everyone else.
• Email the first three. Leave the fourth alone until they opt in.
• Put an unsubscribe in every message, and act on each request the day it arrives.
• Don't hide who you are. The ICO requires a valid contact address so people can opt out.
• A short list that wants to hear from you beats a long one that doesn't, and never more so than at Christmas.

The same regulations turn up from the other end in whether you need a cookie banner for analytics, and if the list lives in somebody else's tool, it's worth knowing who owns your marketing accounts. The rest of this series deals with the client gift, the prize draw and your hours on Google. And if the list is the weak part of your marketing, our 90-day marketing plan works out what to fix first.