{"id":95865,"date":"2026-09-26T09:29:10","date_gmt":"2026-09-26T09:29:10","guid":{"rendered":"https:\/\/mailrelay.com\/?post_type=glossary&p=95865"},"modified":"2026-09-26T09:29:14","modified_gmt":"2026-09-26T09:29:14","slug":"custom-fields","status":"publish","type":"glossary","link":"https:\/\/mailrelay.com\/en\/glossary\/custom-fields\/","title":{"rendered":"Custom fields"},"content":{"rendered":"\n

You have a list of 5,000 contacts. For each one you know the email address and, with luck, the first name. But you don’t know which city they live in, what they bought or when their birthday is. Without that data, everyone gets the same message. Custom fields are how you store that information so you can use it in your campaigns.<\/p>\n\n\n\n

What are custom fields?<\/h2>\n\n\n\n

Custom fields are extra pieces of data you add to each contact’s record, beyond their email address. They work like additional columns in your email database<\/a>: “city”, “last product purchased”, “sign-up date” or “customer tier”, for example.<\/p>\n\n\n\n

Each field has a name, a data type and a tag that your email tool uses to insert it into your messages.<\/p>\n\n\n\n

Don’t confuse them with custom fields in WordPress<\/a>, which add metadata to posts and pages on a website. Here we’re talking about data about your subscribers<\/a>.<\/p>\n\n\n\n

Default fields and custom fields<\/h2>\n\n\n\n

Every email marketing platform comes with a set of built-in fields. In Mailrelay, for example, each contact can already have an email, name, address, city, state or province, country, language, birthday and website.<\/p>\n\n\n\n

Custom fields cover everything else. A training academy will need “course of interest”; a sports shop, “favourite activity”; a software company, “subscribed plan”. You decide which data is useful to you.<\/p>\n\n\n\n

\"Contact<\/figure>\n\n\n\n

Types of custom fields<\/h2>\n\n\n\n

The field type defines what data it accepts and how you can use it later. Choosing it well avoids errors when you import and segment.<\/p>\n\n\n\n

Field type<\/th>What it stores<\/th>Example<\/th>Typical use<\/th><\/tr><\/thead>
Text<\/td>Free words or phrases<\/td>Company: “Lopez Garage”<\/td>Personalizing the greeting or signature<\/td><\/tr>
Number<\/td>Figures<\/td>Loyalty points: 350<\/td>Segmenting by ranges<\/td><\/tr>
Date<\/td>Day, month and year<\/td>Sign-up date: 03\/12\/2026<\/td>Anniversaries and reminders<\/td><\/tr>
Dropdown<\/td>One option from a closed list<\/td>Tier: basic, pro, business<\/td>Clean segments with no variants<\/td><\/tr>
Checkbox<\/td>Yes or no<\/td>Accepts partner offers<\/td>Filtering consents or preferences<\/td><\/tr>
Multiple choice<\/td>Several options at once<\/td>Interests: running, yoga<\/td>Content based on interests<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

A practical tip: whenever you can, use dropdowns instead of free text. If people type their city by hand, you’ll end up with “London”, “london” and “Londn” in the same list.<\/p>\n\n\n\n

And segmenting like that is a headache.<\/p>\n\n\n\n

What custom fields are used for<\/h2>\n\n\n\n

Storing data has no value on its own. The value lies in what you do with it in every send:<\/p>\n\n\n\n