What Is Email Marketing? A Practical Guide to Doing It Right
Email marketing is still the one digital channel that doesn’t depend on someone else’s algorithm. A change at Instagram can wipe out an account’s reach overnight; a subscriber list, on the other hand, is yours. But getting it wrong has real consequences — fines from data protection authorities for mailing bought lists, and campaigns Gmail sends straight to spam because the domain doesn’t meet the technical requirements it has enforced since 2024.
This guide explains what email marketing is, the main types of email, how to build a list lawfully in Europe, what Gmail and Outlook require to reach the inbox, which metrics actually matter, and what it costs to get started.
What email marketing is
Email marketing is the use of email to communicate with people who have given a brand permission to contact them: winning customers, keeping existing ones, sharing news or selling. It’s a form of direct marketing, because it targets a specific audience and aims to trigger an action (a purchase, a sign-up, a visit), and it’s measurable, because every send generates data on who opened, who clicked and who bought.
Its main advantage over social media is ownership. A social audience belongs to the platform, which decides how many of your followers see each post. An email list belongs to whoever builds it: if a network changes its algorithm tomorrow, your subscribers are still there.
Types of email in an email marketing strategy
The newsletter is the best-known format: a regular send (weekly, fortnightly, monthly) with useful content, news or offers, designed to keep the relationship alive even when the subscriber isn’t buying. It works when it offers something readers value in itself; if it only pushes sales, unsubscribes climb fast.
Transactional emails are triggered by something the user does: sign-up confirmation, purchase receipt, shipping notice, password reset. They have the highest open rates because users expect them, and they don’t legally require marketing consent, as long as they don’t turn into disguised advertising.
Automated emails (or sequences) are sent based on behaviour: a welcome series after sign-up, an abandoned-cart reminder, a re-engagement message to someone who hasn’t opened in months. They usually deliver the best return, because they arrive when the message is relevant. Promotional emails, finally, announce a specific offer or launch, and need the most care over frequency to avoid burning out the list.
How to build a subscriber list lawfully
Buying an email database is the fastest way to wreck a strategy. Across the EU, sending marketing emails to people who haven’t consented is unlawful, and it also destroys deliverability: addresses that never asked for your emails mark them as spam, Gmail and Outlook take note, and your sends stop reaching legitimate subscribers too.
A list is built through sign-up forms on your site, in exchange for something of value: a downloadable guide, a welcome discount, access to exclusive content. Double opt-in (the subscriber confirms via a link sent to their inbox) reduces initial volume, but guarantees real addresses, leaves proof of consent and improves your domain’s reputation from the very first send.
What EU law says about email marketing
Two layers of rules apply at once. The GDPR governs how personal data is collected and processed: you must say who is processing the data, for what purpose and for how long. The ePrivacy Directive, in its Article 13, requires prior consent for unsolicited marketing emails to individuals, and each member state transposes it into its own national law.
The same article allows an important exception, often called soft opt-in: a business that obtained a customer’s email in the context of a sale may email them about its own similar products, provided the customer was given the chance to object when their details were collected and in every message afterwards. In all cases, every email must offer a simple, free way to unsubscribe. Enforcement and fines are handled by each country’s data protection authority. This isn’t personalised legal advice.
Deliverability: what Gmail and Outlook now require
Since February 2024, Gmail and Yahoo require anyone sending more than 5,000 emails a day to their users to authenticate their domain with SPF, DKIM and DMARC, offer one-click unsubscribe (processed within two days), and keep the spam complaint rate below 0.3%. Microsoft introduced equivalent authentication requirements for Outlook from May 2025. The official guidance is in Google’s email sender guidelines.
In practice, any serious email marketing tool walks you through setting up SPF, DKIM and DMARC on your domain. It’s an afternoon of technical setup, but without it a significant share of your sends ends up in spam even if your list is spotless.
The metrics that actually matter
Open rate is no longer reliable. Since 2021, Apple Mail Privacy Protection preloads email images, which logs many emails nobody read as “opened”. It’s still useful for comparing your own trends over time, but not as an absolute figure.
The useful metrics are the ones that reflect an action: click rate, conversions (purchases or sign-ups attributed to email), unsubscribe rate and spam complaint rate. A steadily rising unsubscribe rate signals that content or frequency isn’t landing; a complaint rate above 0.1% is a warning sign for deliverability.
Tools and what it costs to start
The most widely used platforms, such as Mailchimp, Brevo, MailerLite or Klaviyo, offer free or entry-level plans for small lists, with prices rising as contacts and sends grow. Starting with a few hundred subscribers can cost nothing; beyond a few thousand, the tool becomes a monthly subscription worth keeping an eye on.
Paying for these subscriptions with a virtual card reserved for business tools makes it easy to see what your marketing stack costs each month, and to cancel a charge without touching your main card when a tool is no longer used. A Bitsa prepaid card lets you hold several virtual cards for exactly this, and the Free plan has no monthly fee.
Email marketing versus social media
They aren’t competing channels. Social media helps people discover you; email keeps the relationship going with those who already know you. A solid strategy uses social to drive traffic to a sign-up form, and email to turn that interest into sales.
Email is also one of the most profitable channels for anyone earning from recommending third-party products: a loyal list converts far better than cold traffic. In both cases the underlying logic is the same: build an audience you own, then give it reasons to stay.
Frequently asked questions about email marketing
Is it legal to buy an email list in Europe?
Buying one isn’t prohibited in itself, but sending marketing emails to those addresses without consent breaches EU rules, and it seriously damages your domain’s reputation with Gmail and Outlook.
Can I send marketing emails to my customers without asking?
Only about your own products or services similar to what they bought, if you gave them the chance to object when collecting their details and keep doing so in every email. Anything else needs explicit consent.
What is double opt-in and is it worth it?
It means asking subscribers to confirm their sign-up via a link sent to their inbox. It slightly reduces sign-up volume, but guarantees real addresses, provides proof of consent and improves deliverability.
Why are my emails landing in spam?
Most often because the domain lacks SPF, DKIM and DMARC, the complaint rate is high, or emails go to addresses that never asked for them. Gmail and Outlook now require authentication from bulk senders.
How often should I send a newsletter?
There’s no universal frequency. What matters is a steady rhythm you can sustain with useful content, while watching the unsubscribe rate: if it rises after you increase frequency, you’re sending too much.