Email campaigns
Email list segmentation
Segmentation means dividing your email list into groups so each receives emails that suit it: new customers and loyal ones, people interested in different products, trade and retail buyers, people who read every email and people who have not opened one in a year. Done simply, it makes emails more relevant and reduces unsubscribes. Done in excess, it multiplies work without much benefit. The key is to start with a few segments that clearly change what you would send.
Below: useful segments, data you need, consent, starting simple, inactive subscribers and measuring the difference.
Illustrative diagram
Useful segments to consider
| Segment | What you would send differently |
|---|---|
| New subscribers | Introduction and best-known products |
| Recent customers | Care tips, related products, review requests |
| Interest groups | Content and offers in their area |
| Trade versus retail | Different prices, terms and products |
| Inactive subscribers | A re-engagement email, then less frequent sends or removal |
A segment must change what you send
The test for a useful segment is simple: would you write a different email for this group? If not, the segment only adds work. Interest-based segments, such as gardening versus cookery customers of a homeware shop, pass the test. Segments based on data you hold but would not act on, such as a postcode area for a national online shop, may not.
Data you need
From sign-up
- Interests chosen by the subscriber
- Where they signed up
From purchases
- What and when they bought
- Customer type, such as trade
From engagement
- Recent clicks
- Last activity date
Consent in every segment
Segmenting does not change whether someone may be emailed. The ICO's guidance says consent or the soft opt-in is normally needed for marketing email to individuals, and the soft opt-in only covers similar products and services. A segment built from customers who never agreed to marketing should not be mailed just because the data exists. Keep consent status attached to each contact and check it is respected whenever a segment is used.
Example: three segments for a garden centre
Illustrative example — not a client case study
Situation: A garden centre sends one monthly email to its whole list.
- Sign-up forms add an interest choice: plants, garden furniture, gifts.
- Monthly emails keep a shared top section and swap the main feature by interest.
- Inactive subscribers receive one check-in email before being mailed less often.
What this shows: Emails became more relevant without tripling the work. This example is illustrative.
Inactive subscribers
Subscribers who have not engaged for a long time may no longer want your emails, and continuing to send to them can increase complaints. Gmail's sender guidelines ask senders to keep spam rates low. A short re-engagement email asking whether they want to stay subscribed, followed by sending less often or removing those who do not respond, keeps the list healthier.
Start simple
Start with two or three segments that clearly change what you send. Use shared templates with one swapped section rather than writing entirely different emails. Add more segments only when results show the extra work is worth it.
Measuring the difference
Compare clicks, purchases and unsubscribes for segmented emails against previous whole-list sends, allowing for seasons and offers. If a segment performs no differently, merge it back.
Keeping segment data accurate
Segments are only as good as the data behind them. Interests chosen at sign-up go out of date, purchase records may not reach the email platform if systems are not connected, and duplicate contacts can land in two segments at once. Check how data flows from your shop, booking system or forms into the platform, decide which source wins when they disagree, and let subscribers update their own interests through a preferences link in every email.
Setting segments up in your platform
Email platforms can let you build segments from tags, fields or activity, and some update them automatically as data changes. Name segments clearly, note what each is for and who uses it, and review the list from time to time so old segments do not pile up unused.
Information to treat with care
Avoid segmenting on sensitive details, such as health information, unless you have checked the rules with your adviser and subscribers would expect it. Information a subscriber has not knowingly shared with you should not be inferred and used to target them.
Questions about email list segmentation
What is email list segmentation?
Dividing your list into groups that receive emails suited to them.
Which segments are most useful?
Ones that change what you send, such as interests or customer type.
Does segmentation change consent?
No; consent or the soft opt-in still applies to each contact.
How many segments should we start with?
Two or three that clearly change the email.
What about inactive subscribers?
Send a re-engagement email, then send less often or remove non-responders.
How do we know segmentation works?
Compare clicks, purchases and unsubscribes with whole-list sends.
Sources referenced
Platform features, guidance and rules change. We check the current versions before committing to an approach. This page is general information, not legal advice.
- ICO: How do we comply with the PECR electronic mail marketing rules? (opens in a new tab) — reviewed 2026-10-29
- Google: Email sender guidelines (opens in a new tab) — reviewed 2026-10-29
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