Contact Properties

String: plan: &quot;enterprise&quot; , job_title: &quot;CTO&quot;
Number: logins_count: 42 , mrr: 1500
Boolean: is_beta_tester: true , onboarding_completed: false
Date (ISO-8601 string): trial_expires_at: &quot;2026-10-01T00:00:00Z&quot;

Custom properties let you store arbitrary metadata on contacts to enable rich personalization in templates and powerful filtering in segments.

Supported Property Types

You can update a contact’s properties using PATCH /api/contacts/:id:

await mailofly.contacts.update("cnt_01J8G52XYZ", {
  properties: {
    plan: "enterprise",
    upgraded_at: new Date().toISOString(),
  },
});

Any custom property attached to a contact can be referenced directly in templates using standard merge tag syntax:

<p>Your current plan: <strong>{{plan | Free}}</strong></p>
<p>Company: {{company}}</p>