A business that wins customers locally accumulates something over the years that appears in no balance sheet: the addresses of people who were once satisfied. Out of that grows the only channel a company truly owns. A search engine can change its ranking, a social network can throttle reach - your own mailing list stays reachable. It is also the channel where a cease-and-desist letter arrives fastest: advertising by email without prior express consent counts as an unreasonable nuisance under Section 7(2)(2) (UWG), and a single message is enough to trigger it (BGH). On top of that comes a technical hurdle: 46.8 percent (Securelist) of global email traffic was spam in December 2023, which is why the large mailbox providers filter hard. From 5,000 messages per day (Google) the largest provider requires SPF, DKIM and DMARC, and since May 2025 (Microsoft) a comparable requirement applies at the second largest. A business with 600 recipients sits below those thresholds, yet the filtering logic behind them assesses every sending domain - including the small one. This article first draws a clean line: it is not about mailboxes and sender addresses, which our article on a professional email address on your own domain covers. It is about advertising sent to many - about consent, proof, unsubscribing, deliverability and a rhythm you can still keep in the third year.
Key takeaways
- The mailing list is the only channel you own: the addresses stay with you, while reach on other platforms depends on someone else's rules.
- Advertising by email requires prior express consent (UWG); the sender owes the proof of it (GDPR), and the double opt-in procedure is the recognised way to provide that proof (BGH).
- For existing customers, Section 7(3) (UWG) allows an exception - but only if all four conditions are met together.
- Deliverability is engineering: sending from your own domain with SPF, DKIM and DMARC, maintained bounce lists and an unsubscribe that takes effect within two days (Google).
- Six careful issues a year tend to achieve more than twelve hasty ones; the measures that count are delivery rate, clicks through to the service page and the enquiries that follow.
The mailing list is the only channel you own
Reach on someone else's platform is borrowed. Anyone who has built up followers there reaches them only as long and as often as the operator's rules permit; if the selection logic changes, access disappears with no right of objection. An email address, by contrast, belongs to the assets of the business. It can be exported, transferred and used regardless of which network currently holds people's attention. If you run both, know the difference: social media for local businesses creates visibility, the mailing list creates commitment. That is why it pays to move attention from borrowed channels into your own, consistently.
The mailing list differs fundamentally from the mailbox, even though both are called email. A business address serves the reply to one person: quotation, follow-up question, invoice. Legally that is correspondence. The mailing list, by contrast, sends an advertising message to many recipients at once, and from that moment competition law applies in full force. For every single address it has to be demonstrable why it is on the list. If domain and mailbox are already set up cleanly, half the technology is in place - the other half consists of proof and process.
A mailing list does not replace the website, it leads back to it. An issue should not explain everything; it should set an occasion and trigger the click through to the matching service page, because that is where the enquiry starts. If you have already put the paths on your website in order, our article on more enquiries through the website shows where to connect them. The reverse also holds: an issue that leads to an unclear page consumes attention without producing anything.
What the list achieves
It reaches people who already know you, at a moment you choose. Reminders about maintenance or check-ups, notes on seasonal stock, changed opening hours around public holidays - occasions nobody actively searches for and which would otherwise go unnoticed.
What it does not replace
It replaces neither a findable website nor search. New customers rarely arrive through the list, because only people who have already been there are on it. As a sole channel it stays too narrow; as a complement it is the steadiest one a business has.
Who benefits from a mailing list - and who hardly does
The question comes down to a single criterion: is there a recurring occasion on which your customers want to hear from you? Where that occasion is missing, filler material appears, and filler material leads to unsubscribes and spam complaints - both of which damage the deliverability of every future issue. Where the occasion is already built into the working year, the list almost writes itself, because the topic is already in the calendar.
Practices and health professions
Check-up and follow-up intervals are plannable and genuinely useful to patients. A short reminder about the upcoming appointment, together with a note on how to book, is a service to the patient - and fills the calendar in quiet weeks.
Trades and technical services
Maintenance intervals, inspection deadlines and seasonal work set the pace. A reminder about the heating service in autumn and the air conditioning in spring is not advertising but information that was due anyway.
Retail and hospitality
Seasonal stock, promotional weeks and changed opening hours are short-lived and sit awkwardly on a website meant to hold true permanently. The mailing list is where they belong, because they arrive at the moment they are useful.
The effort rarely pays off where a customer makes a one-off decision and then needs nothing for years - a bathroom renovation, a removal job, or the emergency service called only in a crisis. Here every hour invested in findability returns more than one spent on a mailing list. Likewise, anyone who cannot spare 60 minutes a quarter for content is better served by the website and online appointment booking than by a list that falls silent after the third issue. A dormant list is worse than none at all: writing again after two years of silence frequently results in spam complaints - and damages the reputation of your own sending domain.
| Starting point | A mailing list pays off | Website and search are better |
|---|---|---|
| Occasion | Recurring: maintenance, check-ups, season | One-off: renovation, removal, emergency |
| Customer base | Many returning customers | Mostly new customers from search |
| Time budget | 60 minutes a quarter are secured | No fixed time available for content |
| Legal basis | Consents are on file with a log | Addresses of undocumented origin |
| Goal | Retention, repeat business, capacity | First contact and visibility |
Consent and double opt-in: the proof you keep
The legal basis for sending is consent under Article 6(1)(a) (GDPR), and Article 7(1) (GDPR) requires the controller to be able to demonstrate it. Demonstrating means: in a dispute you show who agreed, when, in what wording and by which route. An address list without those details is not proof but an assertion. So the question is not whether you keep a log, but how cleanly - and whether you could produce that log within an hour if it came to it.
The double opt-in procedure solves this in practice: after the entry in the signup field, a confirmation email goes to the address given, and only the click inside it activates the entry. That simultaneously demonstrates that the address belongs to the person who signed up and was not entered by a third party. The Federal Court of Justice has recognised this procedure as a way of documenting consent (BGH). The confirmation email itself must contain no advertising - it is purely procedural. Technically the process resembles consent management for cookies under the GDPR; legally it is a separate case with separate proof. The supervisory authorities have summarised their requirements for direct marketing in a dedicated guidance document (Datenschutzkonferenz).
- The timestamp of the signup and the timestamp of the confirmation click, stored separately.
- The full wording of the consent declaration in the version that applied at the time of signup.
- The origin of the signup: which page, which form, which occasion.
- The technical identifier of the confirmation click, so the transaction can later be attributed unambiguously.
- The time and route of any later withdrawal - Article 7(3) (GDPR) requires it to be as easy to withdraw as it was to give.
- A version number for the consent text, so later changes remain traceable.
Where the addresses come from decides everything
Existing customers under Section 7 UWG: the four conditions
There is an exception, and it is often read too generously. Section 7(3) (UWG) permits email advertising to existing customers without prior consent - but only if four conditions are met together. If one of them falls away, the principle in subsection 2(2) applies again and the message is an unreasonable nuisance. The four conditions sit side by side in the statute and read, in substance, as follows:
- You received the email address from the customer directly, in connection with the sale of goods or a service - not from a directory, not via a third party, not from a mere enquiry that led to no contract.
- You advertise exclusively your own, similar goods or services. The heating installer may send a reminder about servicing the system they fitted; an unrelated offer falls outside.
- The customer has not objected to the use. An objection once declared applies permanently and has to be stored reliably, including across a change of systems.
- You point out clearly, both when collecting the address and in every single use, that the customer may object at any time without incurring any costs beyond the basic transmission rates.
In practice the exception mostly fails on points two and four. Similar is to be read narrowly: someone who fitted windows may lawfully advertise their servicing, not a new photovoltaic system. And the objection notice has to appear twice - when the address is collected and in every single email. If you rely on the exception, keep those addresses technically separate from the consent addresses, because the two groups may receive different things. A mixed list is hard to untangle afterwards.
Two groups, one interface
Unsubscribe and mandatory details in the footer
Every marketing email needs an unsubscribe that works without obstacles. Article 7(3) (GDPR) requires withdrawal to be as easy as giving consent; a login, a contact form or a reply email with a keyword do not meet that. Technically, one-click unsubscribe via the List-Unsubscribe header under RFC 8058 (IETF) has become the standard; the largest mailbox provider requires it for marketing email and expects an unsubscribe to be processed within two days (Google). Acting faster collects fewer complaints.
Unsubscribe link
Visible in the footer of every issue, not hidden in pale grey small print. One click is enough, no confirmation dialogue, no login. The unsubscribe takes effect immediately and for every list the address appears on.
Provider details
Name, address and contact details belong in the footer, and for legal entities the legal form and authorised representatives as well - the same details Section 5 (DDG) requires for the website. What belongs in the legal notice under the DDG belongs here too.
Reason for the mailing
One sentence on why the recipient is getting this email: signed up on 12 March via the form on the website, or maintenance contract since 2023. That removes the basis for complaints and answers the most frequent question in advance.
Equally important is what happens after an unsubscribe. The address leaves the send list but stays stored as a suppression entry, so it does not reappear by accident during the next data migration. Bounce maintenance runs separately: hard-rejected addresses are removed after the first failure, soft-rejected ones after several unsuccessful delivery attempts. Dead entries that have not reacted to anything for twelve months get one final query and are then deleted. A small, well-maintained list delivers better than a large one full of dead addresses - and costs less to send.
Deliverability: sending from your own domain
The sender of an issue should be your own domain, not a shared address. Three entries in the name service decide whether the mailbox providers accept the message: SPF defines which servers may send for your domain; DKIM signs every message cryptographically; DMARC determines what happens to messages that do not survive those checks. How the three entries work together is described in detail in our article on email setup with your own domain. For a mailing list there is one addition: the domain that passes the checks has to match the address in the From field - otherwise attribution fails despite valid entries.
The requirements have become more binding since 2024. Anyone sending 5,000 messages per day (Google) or more to personal mailboxes at the largest provider has to present SPF, DKIM and DMARC, send over TLS and hold a valid reverse entry in the name service; the spam complaint rate should stay below 0.10 percent (Google) and should not reach the 0.30 percent (Google) mark. Since May 2025 (Microsoft) the second largest provider likewise requires the same three entries from senders above 5,000 messages a day and initially sorts messages without valid checks into the junk folder. Smaller businesses sit below that threshold - the checks still run, only without the hard enforcement. Meeting them gives you the quieter inbox.
- Your own sending domain with valid SPF, DKIM and DMARC entries, aligned with the address in the From field.
- A separate subdomain for marketing sends, so complaints do not carry over to your business correspondence.
- A plain-text version alongside the designed one, because some mailboxes display only that.
- Images with alternative text and the core message as text, since many mailboxes load images only on request.
- Keep the total size modest and send no attachments; a link to the website replaces any enclosure.
- Check the rendering on a phone before the issue goes out - that is where the larger share is read.
Read on a phone, decided on a phone
Rhythm and the metrics that actually count
The most common mistake at the start is an over-ambitious cadence. Twelve issues a year sound committed but quickly lead to issues without an occasion. Six careful issues, each with a genuine reason, tend to achieve more: they get read, they get unsubscribed from less often, and they can realistically be produced alongside daily business. Tie the cadence to your working year - heating service in September, check-up reminder in January, season opening in April. A topic plan for twelve months, drawn up once a year, takes the pressure off each individual issue.
Delivery rate
The share of messages that were accepted at all. If it drops, the cause is usually technical or a stale address list, not the content. Check this figure first, before you start polishing subject lines.
Clicks to the service page
Not every click counts equally. The interesting one is the click that lands on the matching service page - it shows that the occasion was understood and that the bridge to the website holds.
Enquiries that followed
The only figure that counts in the end. Tag the links coming from the mailing list so you can say afterwards which issue triggered which enquiry.
The open rate is deliberately absent from this list. Since the large mailbox providers preload images in the background to protect their users, sending reports show opens that did not happen that way. As a rough trend across many issues the figure still has some use; as a measure of success for a single issue it no longer does. What holds up is what happens next: the click and the enquiry. Once the click lands on a service page, a website assistant that pre-qualifies enquiries can pick up the open questions right there instead of sending the visitor back to the search box.
The figure that is not in the sending report
From the signup field to editorial upkeep
Building the list starts on the website, not in the sending tool. A signup field belongs where someone is already satisfied: below a helpful article, on the confirmation page after an appointment booking, in the footer. Two fields are enough - address and consent checkbox - with one sentence above them saying what the recipient gets and how often. If you announce six issues a year, send six. The box stays empty, the text beside it names the purpose and the right of withdrawal. If part of your customer base speaks English, add a language field; when that effort pays off is covered in the article on the bilingual website.
Next comes the confirmation path: confirmation email, confirmation page, log entry. All three parts belong on your own domain, so the consent is documented where it will later be needed - and so you still hold the proof if you ever change sending tools. The confirmation page is also a good opportunity to deliver the first bit of value: a pointer to the matching guide, the consulting hours or the next maintenance window.
In terms of content, the mailing list lives on a topic plan drawn from the same source as the website content. What answers search queries as a guide article becomes the occasion in the mailing list - that interplay is described in our article on content marketing for local businesses. In the content marketing package we plan both together, so a topic works twice: once in search and once in the inbox.
That leaves the question of time. The signup field, the confirmation path and the entries for SPF, DKIM and DMARC are set up once; after that the ongoing effort is manageable, but it does not disappear. When daily business leaves no room, we take over editing, sending and evaluation as part of ongoing website care - topic plan, copy, technical checks and a look at the enquiries that followed. What makes sense for your business is something we work out in a short conversation.
A mailing list is not an advertising channel but a promise: you get in touch when there is something to say - and stay quiet when there is not.
List, mailbox and website share one domain
Sources and Studies