Your Emails Keep Landing in Spam? The Deliverability Guide (SPF, DKIM, DMARC)

You send a proposal to a prospect in Geneva, an invoice to a loyal client or your monthly newsletter… and hear nothing back. The problem is often not your message: it simply never reached the inbox. In 2026, roughly one commercial email in six ends up in the spam folder or vanishes altogether. For an SME in French-speaking Switzerland, that means quotes that are never read, follow-ups that go unanswered and revenue that quietly evaporates. The good news: deliverability follows precise technical rules — SPF, DKIM, DMARC, domain reputation, warmup — and they can all be mastered. This guide explains them in plain language, with concrete actions you can take today.

The real cost of a spammed email for a Swiss SME

Let's put numbers on it. A fiduciary firm in Lausanne sends 2,000 emails per month: proposals, appointment reminders, a newsletter. If 15% land in spam, that is 300 lost messages every month. With an average conversion rate of 2% and an average order value of CHF 800, the loss exceeds CHF 4,800 per month — close to CHF 58,000 per year. And that is before counting unseen invoices that delay payments and missed appointments that leave holes in the calendar.

Since Google and Yahoo tightened their sender requirements (mandatory authentication, complaint rate below 0.3%), mailbox providers no longer give anyone the benefit of the doubt, and Microsoft has followed suit with Outlook. A poorly configured domain is treated as suspicious by default. In other words: without SPF, DKIM and DMARC properly in place, your emails start with a handicap before a single word is written.

SPF, DKIM and DMARC explained simply

These three acronyms sound intimidating, but the underlying idea is very simple: prove to mailbox providers that the email really comes from you, not from an impostor. Think of it as sending official registered mail.

SPF: the list of authorised senders

SPF (Sender Policy Framework) is a list published in your domain's DNS zone that declares: "these are the servers allowed to send email on behalf of mydomain.ch". If an unknown server tries to send using your address, the recipient's mailbox provider spots it immediately. It is the equivalent of an official list of spokespeople. A typical SPF record looks like v=spf1 include:_spf.google.com include:spf.brevo.com -all. Classic trap: SPF only tolerates 10 DNS lookups; beyond that, the record silently becomes invalid.

DKIM: the digital wax seal

DKIM (DomainKeys Identified Mail) adds an invisible cryptographic signature to every email you send. The recipient's mailbox provider verifies this seal against a public key published in your DNS. If the content was altered in transit, or if the signature is missing, suspicion kicks in. It is the wax seal on the envelope: intact, it proves both the sender's authenticity and the message's integrity.

DMARC: the instructions in case of fraud

DMARC (Domain-based Message Authentication, Reporting and Conformance) is the command layer. It tells mailbox providers what to do when SPF or DKIM fail: do nothing (p=none), quarantine (p=quarantine) or reject (p=reject). It also sends you daily reports revealing who is sending email under your domain name — including fraudsters you never suspected. The right approach: start with p=none to observe for two to four weeks, move to p=quarantine, then to p=reject once everything is clean. A domain at p=reject is nearly impossible to spoof: your clients are protected from phishing sent in your name.

Check your configuration in 10 minutes

No network engineering degree required. Here is the express check we run for every new client:

1. Send a test email to a Gmail account, open the received message and click "Show original". Three lines must display PASS: SPF, DKIM and DMARC. A single FAIL and you have found the culprit.
2. Run an online test such as mail-tester.com: send it an email and it returns a score out of 10 with a breakdown of every issue. Aim for at least 9/10.
3. Check your DNS records with a tool like MXToolbox: look up SPF, DKIM and DMARC on your domain and make sure there are no duplicates or syntax errors.
4. Sign up for Google Postmaster Tools (free) to continuously monitor your domain reputation as Gmail sees it.

A crucial point for SMEs: every tool that sends on your behalf must be covered. Your main mailbox (Google Workspace or Microsoft 365), your newsletter platform (Brevo, Mailchimp), your CRM, and also your website. The most frequent oversight we see among our Swiss clients: the WordPress contact form sending unauthenticated notifications — which land in spam and make you believe that "nobody ever fills in the form".

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Domain reputation: your digital track record

Authentication is the entry ticket, not a guarantee of reaching the inbox. Mailbox providers assign your domain (and your sending IP address) a reputation score based on how recipients actually behave: do they open your messages? Do they report them as spam? Do your emails bounce off non-existent addresses?

• Complaint rate: stay below 0.1% (one complaint per 1,000 emails). Above 0.3%, Gmail sends you to spam almost systematically.
• Bounce rate: below 2%. Clean your list regularly: addresses inactive for twelve months, typos, employees who have left.
• Engagement: recipients who open, click and reply improve your reputation. A simple trick: ask a genuine question in your first email and explicitly invite a reply.

Reputation builds slowly and collapses fast. A single mass send to a purchased list can wipe out months of effort. A useful reminder: in Switzerland, email prospecting requires prior consent (Unfair Competition Act) and the revised Data Protection Act provides for fines of up to CHF 250,000. Purchased lists are both a legal risk and poison for your deliverability.

Warmup: heat up your domain before you accelerate

A domain or address that has never sent significant volumes is a stranger to mailbox providers. If it jumps from 10 emails a day to 5,000 overnight, red alert: that is the textbook behaviour of a spammer. Warmup means increasing volume gradually to build trust.

A typical plan for a new domain or a new sending platform:

• Weeks 1-2: 20 to 50 emails per day, to your most engaged contacts (active clients, partners) who will open and reply.
• Weeks 3-4: 100 to 300 emails per day, keeping a close eye on complaints and bounces.
• From week 5: double the volume each week until you reach your target, as long as the indicators stay green.

Pro tip: for cold outreach, use a dedicated domain or subdomain (for example news.mydomain.ch). If its reputation deteriorates, your main domain — the one carrying your invoices and client correspondence — remains untouched.

The 7 mistakes that send you to spam

1. Two SPF records on the same domain: the standard forbids it, the result is invalid and everything fails silently.
2. DMARC missing or stuck at p=none forever: you are not protected against spoofing, and mailbox providers can see it.
3. Sending from a free address (@gmail.com, @bluewin.ch) for your business: your brand cannot be properly authenticated, and your image suffers.
4. Never cleaning your list: dead addresses inflate your bounce rate, and spam traps often hide among them.
5. No visible unsubscribe link: recipients click "Report as spam" instead — the worst possible signal. It is also a legal requirement in Switzerland.
6. Too many images and too little text, shortened links such as bit.ly, subject lines in capitals with exclamation marks: all of them trigger the filters.
7. Erratic sending volume: nothing for two months, then 3,000 emails at once. Consistency reassures the algorithms; unpredictability alarms them.

Your deliverability action plan

To sum up in five steps: check SPF, DKIM and DMARC today (10 minutes); fix the configuration for every sending tool, contact form included; clean your list and set aside inactive contacts; adopt a steady, gradual sending rhythm; monitor your reputation every month with Postmaster Tools. The typical result we see with our clients: inbox placement rising from 75-85% to over 95% within four to six weeks. On a base of 2,000 monthly sends, that is often the difference between a loss-making campaign and several thousand francs of additional revenue.

At Digital Swiss Agency, we configure your domain's full authentication, set up monitoring and manage your email campaigns end to end — so your messages finally reach the people they were written for.

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