Lettr + Stream Deck

Attach every combination of 1-1000 contacts and 1-50 audience lists, processing up to 50,000 contact-list pairs and reporting new and existing memberships.

Create or recognize up to 1000 normalized, deduplicated contacts. Shared properties affect only newly created contacts; list_id applies to all contacts, including those that already exist.

Cancel a scheduled email before its delivery time; cancellation is unavailable once processing has begun.

Create one audience contact with optional properties and list membership.

Create an unverified audience contact and irreversibly send an external confirmation email; the contact becomes subscribed only after confirming.

Create a uniquely named audience list for grouping contacts.

Define a custom contact property with an immutable name and value type. Changing either later requires deleting and recreating the property.

Create a dynamic audience segment whose condition groups are ANDed while conditions inside each group are ORed.