Lettr

Create audience topic

Create a public or private subscription topic with an immutable opt-in or opt-out default.

Create domain

Register a sending domain and return the DNS configuration needed to verify it.

Create template

Create and publish an email template from either custom HTML or Topol editor JSON, extracting its merge tags.

Create webhook

Create an active event webhook using no authentication, HTTP Basic credentials, or OAuth 2 client credentials.

Delete audience contact

Permanently delete one audience contact and its associated memberships.

Delete audience lists

Permanently delete between 1 and 50 audience lists in one request.

Delete audience property

Permanently delete a custom contact-property definition.

Delete audience segment

Permanently delete one dynamic audience segment.

Delete audience topic

Permanently delete one audience subscription topic.

Delete domain

Permanently remove a sending domain from Lettr and SparkPost so it can no longer send email.

Delete template

Permanently delete an email template and all of its versions.

Delete webhook

Permanently remove a webhook so Lettr stops delivering events to it.

Detach contacts from lists

Detach every combination of 1-1000 contacts and 1-50 audience lists, reporting removed and absent memberships.

Get audience contact

Retrieve one contact's email, status, custom properties, list memberships, and topic subscriptions by ID.

Get audience list

Retrieve one audience list and its current contact count by ID.

Get audience property

Retrieve one custom contact-property definition and its fallback value.

Get audience segment

Retrieve one dynamic segment's list restriction, complete AND-of-OR condition definition, and cached contact count.

Get audience topic

Retrieve one subscription topic's defaults, visibility, and current contact count.

Get campaign

Retrieve one campaign's name, subject, sender and reply-to configuration, schedule, rendered HTML, lifecycle state, recipient counts, and engagement statistics.

Get domain

Retrieve one sending domain's send readiness, DNS records, provider detection, and verification status.

Get email

Retrieve a sent email's delivery state, recipients, schedule metadata, and events by request ID.

Get scheduled email

Retrieve a scheduled email's current state and events by transmission ID, including after it has been processed.

Get template

Retrieve an email template's metadata, active HTML or editor JSON content, and version counts by slug.

Get template merge tags

Return required and optional merge tags for a template's active or specified version before sending with substitution data.

Get webhook

Retrieve one webhook's target, enabled state, event selection, authentication mode, and latest delivery status.

List audience contacts

Return one cursor-controlled page of contacts, optionally filtered by search text, status, list, or segment.

List audience lists

Return one cursor-controlled page of audience lists with each list's contact count.

List audience properties

Return one cursor-controlled page of custom contact-property definitions and fallback values.

List audience segments

Return one cursor-controlled page of dynamic audience segments, including their complete AND-of-OR condition definitions, optionally filtered by list.

List audience topics

Return one cursor-controlled page of subscription topics with defaults, visibility, and contact counts.

List campaign events

Return one cursor-controlled page of a campaign's delivery and engagement events, with event, recipient, and time filters.

List campaigns

Return one cursor-controlled page of campaigns with complete delivery and engagement statistics, optionally filtered by lifecycle status.

List domains

Return all sending domains with approval, DNS verification, and send-readiness status.

List email events

Return one cursor-controlled page of delivery and engagement events across sent emails, with event, recipient, transmission, bounce, and date filters.

List emails

Return one cursor-controlled page of sent emails, optionally filtered by recipient and date range.

List projects

Return one cursor-controlled page of Lettr projects and their IDs for use with template operations.

List templates

Return one cursor-controlled page of email templates for a project or the team's default project.

List webhooks

Return all event webhooks with target, enabled state, event selection, authentication mode, and latest delivery status.

Publish template version

Create and activate a new version of an existing email template from exactly one of HTML or Topol editor JSON, optionally renaming the template atomically.

Schedule campaign

Schedule a campaign for future delivery or reschedule it.

Schedule email

Create a transactional email scheduled 5 minutes to 3 days in the future; it remains cancellable until processed.

Send campaign

Immediately and irreversibly start sending a sendable draft campaign to its resolved audience.

Send email

Immediately queue a transactional email to up to 50 recipients using inline content or a Lettr template.

Unschedule campaign

Cancel a scheduled campaign send and return the campaign to draft.

Update audience contact

Change a contact's email, subscribed or unsubscribed status, or selected custom property values.

Update audience list

Rename an audience list while preserving its contacts.

Update audience property

Set or clear a custom contact property's fallback value.

Update audience segment

Change a dynamic segment's name, optional audience-list restriction, or complete AND-of-OR condition definition.

Update audience topic

Change a subscription topic's name, description, or public/private visibility.

Update template

Rename an email template's metadata without publishing a new version.

Update webhook

Partially update a webhook's name, callback URL, authentication, selected events, or active state.

Verify domain

Run Lettr's DNS verification for a registered domain and return DKIM, CNAME, DMARC, SPF, and ownership results.