Large audiences

A large send is a sequence of decisions: who qualifies, which data the message uses, whether the rendered content is ready, and whether each recipient remains eligible for delivery. A segment count answers only the first question.

Use a broadcast for one campaign sent to a selected contact audience. Prepare the audience and content together, then inspect the send's actual progress and recipient outcomes.

For a seasonal launch, first review a frequent buyer, an occasional buyer and a customer with sparse history. The useful result is a campaign whose audience rule includes the intended customers, whose content handles each case, and whose estimate you can assess. Send a broadcast provides the setup steps; this page explains what changes as the audience grows.

Pick the audience

Choose the Contact schema and an optional saved Segment when creating the broadcast. Review the Audience tab afterward, or generate a custom filter for this campaign. No segment or filter means the whole selected schema, so make that choice deliberately.

Check known inclusions and exclusions in the segment preview. A count can change as source records change before preparation. The send later seals its selected record membership and destination addresses; subsequent segment changes do not continuously add recipients to that broadcast.

The preparation step deduplicates both contact identities and normalized destinations within the broadcast. Multiple records pointing to the same delivery address therefore do not imply multiple messages for that send.

Send it, or schedule it

Complete the email, sender, subject and audience, then review readiness and schedule or start the broadcast. The send captures a revision of its content, brand settings, audience rule, data definitions and quality policy. Editing a separate source after that does not silently rewrite the revision already being processed.

Preparation and content checks happen before recipient delivery. A large campaign can still be preparing or checking content even though its send time has arrived. Review the visible phase and any reason it is waiting instead of repeatedly starting another copy.

Before preparation starts, Cancel send returns the scheduled campaign to an unscheduled state. After preparation starts, Stop sending cancels eligible unsent work; an email already in flight may still arrive. A finished, non-stopped campaign can offer Retry for failed recipients with no attempted send, or Close remaining work to end that work. This does not resend accepted or unconfirmed messages and cannot resume a stopped campaign. Use the broadcast lifecycle reference for the action available in the actual state.

What changes at volume

A large audience increases rendering, lookup and delivery work. If the space runs out of credits, the current broadcast pipeline pauses for credits; waiting recipients are not all converted into terminal failures just because the balance reached zero. Review the reason and billing state before treating a pause as failed delivery.

Select Evaluated fields in the email's Data tab. On-demand relationships perform their lookups for the recipients that need them; unnecessary nested relationships multiply that work. Narrow lists in their definitions and give missing values meaningful content fallbacks.

Scheduled Evaluated fields read published background results. A broadcast revision captures its selected generation, freshness policy and observation time when that context is first established. A later refresh does not replace the selection halfway through the revision. Enabled fields with no complete or expired publication block expansion; paused fields can retain the captured last-published policy. A valid publication with no result for a particular contact can return null. Verify Published value, Data through and the status before starting a campaign that depends on recent event history.

Use the current billing and usage reference for plan allowances and metered work. Audience size alone does not describe the cost of AI generation, nested data reads or the complete delivery path.

Watch it go out

Follow the broadcast's phase and readiness or failure reason. Keep campaign-level preparation separate from the result of each email.

• Metrics shows campaign timing and aggregate delivery and engagement. Use Refresh to request updated metrics.
• Emails shows recipient rows and their current status. Open a row to inspect the message and its activity.
• A credit pause, content-quality pause or campaign failure needs a different response from one recipient's bounce, rejection or suppression.

A segment match is not the final send count. Marketing eligibility also checks email presence, channel subscription and the chosen topic; applicable suppressions and current delivery conditions can prevent dispatch. An individual email’s Sent status means provider acceptance; delivery and engagement arrive as separate feedback. Campaign funnel totals have a different scope; see report definitions.

When a recipient's outcome is uncertain, inspect that specific attempt. Starting a second broadcast or changing occurrence identifiers can create another delivery intent; it is not a diagnostic refresh. The Broadcasts API exposes the supported campaign operations and status data.

Before you send to a big list

Verify the sending domain, test representative data and missing-value cases, and inspect the campaign's readiness checks. A small live audience can help validate source data and resulting messages before a wider campaign, but it has its own delivery and consent consequences.

After sending, review delivery feedback and Postmaster alongside campaign engagement. Use the evidence to improve the next audience or message rather than treating opens as proof that every selected contact received it.

Related

• Broadcasts: the complete send lifecycle and recovery controls.
• Segments: the audience definition and preview.
• Attribute expansion: data selection and generation snapshots.
• Templates: reusable messages invoked for individual recipients.