- Contacts: individual email addresses
- Properties: custom properties for your Contacts
- Segments: groups of Contacts for your organization
- Topics: user-facing tools for managing email preferences

Contacts
Contacts in Resend are global entities linked to a specific email address.
- is associated with a single email address
- can have custom properties
- can be in zero, one or multiple Segments
- can be opted in or out of Topics
Properties
Contact Properties can be used to store additional information about your Contacts and then personalize your Broadcasts.
first_name: The first name of the contact.last_name: The last name of the contact.unsubscribed: Whether the contact is unsubscribed from all Broadcasts.email: The email address of the contact.
Segments
Segments are groups of Contacts for your organization. You can use Segments to send emails to a specific group of Contacts using Broadcasts.
Topics
Topics are user-facing tools for managing email preferences. You can use them to manage your Contacts’ email preferences.
You can customize your unsubscribe page with your
branding from your team settings.