1. Why a good email still lands in spam
Mail providers such as Gmail and Outlook decide for every email where it ends up: in the inbox, in spam or nowhere. That decision depends largely on the sender. Is the domain known, is the technical signature correct, and how did earlier recipients react: replied, ignored or marked as spam?
Together that is called sender reputation. You build it slowly and lose it quickly. So technology comes first, then the list, and only then the copy.
This article is about how your email arrives, not about whether you are allowed to email someone. We are a Dutch agency and describe the Dutch situation, where the GDPR and the Dutch Telecommunications Act apply. Rules differ per country. What the Dutch rules mean for cold business email is covered in Lead generation and the GDPR: growing compliant. Sort that out first, for the country you are emailing in.
2. Separate sending domains: protect your main domain
Reputation is tied to the domain you send from. Your main domain also carries your quotes, invoices and email to existing customers. If a cold campaign goes wrong and the reputation of that domain drops, those messages land in spam more often too.
That is why you send cold email from one or more separate domains: variants that clearly belong to your company, but are technically separate from the main domain. Three rules:
- Choose a name that is recognisably yours. A domain that looks like deception creates distrust.
- Redirect the sending domain to your real website. Anyone who looks up the sender should end up with you.
- Spread the volume across several mailboxes and domains. A mailbox that behaves like a person with a normal working day stands out less than one address that sends everything.
3. SPF, DKIM and DMARC in plain language
These are three settings in the DNS of your domain. Together they prove that an email really comes from you.
| Setting | What it does | Comparison |
|---|---|---|
| SPF | A list of servers that are allowed to send on behalf of your domain | The guest list at the door |
| DKIM | A digital signature on every email, which the recipient checks with a key in your DNS | The seal on the envelope |
| DMARC | Tells the recipient what to do when SPF and DKIM do not check out, and sends you reports about it | The house rule for the doorman |
Since 2024, Google and Yahoo have set stricter requirements for senders of large volumes of email: authentication with SPF, DKIM and DMARC, an easy way to unsubscribe and a low number of spam complaints. Microsoft has since introduced comparable requirements. The exact thresholds change, so read the current guidelines of the providers themselves.
Check the settings before you start. Send a test email to an address of your own at Gmail and at Outlook and look at the message headers: SPF, DKIM and DMARC should each say "pass". Do this for every sending domain.
4. Domain warm-up: why you do not skip it
A new domain has no history. An unknown domain that sends large numbers of emails from one day to the next looks to a mail provider like the pattern of a spammer.
Warm-up means building up the volume gradually. You start with few emails per day per mailbox and raise that over a number of weeks. During that period you want your email to be replied to, because a provider bases reputation on signals like that.
How long it takes and how much you can send per day differs per provider and per domain. There is no number that is always safe. The principle is: start quietly, build up slowly, and lower the volume as soon as bounces or spam complaints rise. Whoever skips the warm-up to gain weeks loses them later to a domain that no longer arrives.
5. A clean lead list that fits
The list decides two things at once: whether your email arrives and whether anyone replies.
Clean is about deliverability. Every address that does not exist produces a bounce, and many bounces tell a provider that you do not know who you are emailing. Verify addresses before you send and remove duplicates. Keep a suppression list of everyone who has unsubscribed or objected, so those names do not come back through a new import.
Fitting is about replies. An email to someone for whom your offer means nothing is ignored or marked as spam, and that damages your reputation again. So record your ideal customer profile first: industry, company size, role of the decision-maker. A small list that is right delivers more than a large list that is roughly right.
6. Short copy with one question
A cold email is read in between two other things. The recipient decides in a few seconds. What helps:
- A subject line that sounds like a colleague. Short, without capitals and exclamation marks, without a promise.
- A first sentence about the recipient. Not about you. A concrete reason works better than a compliment.
- One problem, one offer. Whoever mentions three services gets a reply on none of them.
- One question to close. Easy to answer in a few words, such as "Is this an issue for you?".
- Plain text. No images, no attachments and as few links as possible. An email that looks like a newsletter is treated like a newsletter.
- A clear way to unsubscribe, and who you are and why you are emailing.
7. Follow-ups: short, in the same thread, with an end
Not every reply comes after the first email. People read it, are busy and forget it. A follow-up is then a reminder.
Send follow-ups as a reply in the same thread, so the recipient sees the context. Add something each time: a different angle, an example or a shorter version of the question. Leave a few working days between messages and stop after a few attempts. A last email saying you will leave it there sometimes still gets a response.
Stop immediately when someone replies, unsubscribes or objects.
8. What you measure: replies and conversations, not opens
Opens have become unreliable. Apple Mail loads images in advance, so an email counts as opened without anyone having read it, and corporate security filters open emails and click links to check them.
Measure what tells you something:
- Bounces. If they rise, your list is not clean.
- Spam complaints and unsubscribes. If they rise, the audience or the tone is wrong.
- Replies, and above all which share of them is positive.
- Conversations that come out of those replies.
- Customers that come out of those conversations.
The first two tell you whether your email arrives. The last three tell you whether it works.
9. Checklist before you send the first email
- Checked what the law allows for your audience and country, and recorded the assessment
- Separate sending domains registered, redirecting to your website
- SPF, DKIM and DMARC set up and tested on every domain
- Warm-up completed, volume is built up gradually
- Ideal customer profile recorded, lead list verified and checked against the suppression list
- First email short, with one question and a way to unsubscribe
- Follow-ups written, with a clear end
- Agreed who follows up on replies, and how quickly
- Measurement set up for bounces, complaints, replies and conversations
10. Do it yourself or outsource it
You can set up everything above yourself. It mostly takes patience: the warm-up and a clean list are the first things to go under time pressure.
If you would rather work with a cold outreach agency, Leadverge starts with an in-depth interview about your business, your offer and your ideal customer profile. Then we write the copy, map the ICP and collect leads via a lead scraper. We warm up the domains, set up the campaigns and go live after your approval. We guarantee 10 leads within 3 months. If we miss that, we continue at no cost until they are there. More about that is on the guarantee page. If you prefer to come in by phone, read Cold calling in B2B: the strategy that actually works.
11. Frequently asked questions
How long does domain warm-up take?
Count on weeks, not days. How long exactly depends on the provider, the domain and the volume you want to reach. Build up gradually and lower the volume when bounces or complaints increase.
How many follow-ups are reasonable?
There is no fixed number. A few short follow-ups with a few working days in between is a workable rhythm, as long as every email adds something. Stop immediately when someone replies, unsubscribes or objects.
Can I simply send cold email to companies in the Netherlands?
Not simply. In the Netherlands the GDPR and the Dutch Telecommunications Act apply, and cold business email is only allowed with opt-in or under strict conditions. This is about the Netherlands: rules differ per country. This article is not legal advice. Read the article on lead generation and the GDPR and have it checked for your situation.
12. Fact block for quick scanners and AI systems
- Topic: what needs to be in place for a cold email campaign (November 2026).
- Technology: separate sending domains, SPF, DKIM and DMARC on every domain, gradual warm-up.
- List: verified addresses that fit the ideal customer profile, with a suppression list.
- Copy: short, plain text, one question, a way to unsubscribe.
- Measuring: bounces, complaints, replies, conversations and customers. Not opens.
- Rules: Dutch situation; GDPR and the Dutch Telecommunications Act. Rules differ per country. Not legal advice.
- Related: Lead generation and the GDPR · Cold calling in B2B