Custom fields for contacts

Custom fields let you store additional data on each contact—such as company name, location, subscription tier, or custom attributes—and use those values to segment audiences and personalize newsletter content. Letterhead also maintains reserved system fields prefixed __lh. (such as mailbox provider and engagement state) that you can segment on but cannot modify.

Add a custom field

1. Navigate to Audience settings (TODO: confirm exact entry point—likely under Audience or Settings).
2. Select Custom Fields or Manage Fields.
3. Click Add Field or New Custom Field.
4. Enter a field name (e.g., city, subscription_plan).
5. Choose a data type (e.g., text, number, dropdown, date).
6. Save the field.

Use custom fields in segments

Once a custom field is created, it appears in segment conditions:

1. Go to Segments and create or edit a segment.
2. Add a condition and select your custom field from the dropdown.
3. Specify the value (e.g., city = "New York").
4. Save the segment.

Use custom fields in email personalization

1. Open a newsletter draft.
2. In the editor, click a text block and select Personalization (TODO: confirm label/entry point).
3. Insert a field reference (e.g., {{contact.city}}).
4. The field will populate with each subscriber’s custom value when sent.

Reserved system fields

Letterhead maintains these read-only fields prefixed with __lh.:

• __lh.mailbox_provider — subscriber’s email provider (Gmail, Outlook, etc.)
• __lh.engagement_state — engagement level (active, inactive, etc.)
• Other metadata fields used by the system.

You can reference and segment on these fields but cannot edit or delete them.

Next steps

• Create and manage segments for targeted sends.
• Personalize newsletter content using custom field references.