Follow the message lifecycle
Acceptance reserves recipient quota and returns queued. Workers move through processing and submitted. Only provider delivery events produce delivered. Recipient records have separate status, so a mixed multi-recipient message may be submitted or bounced while another recipient delivered. needs_review means an uncertain submission requires operator reconciliation; do not resend blindly. Cancellation is possible only before worker claiming.
GET /emails/:id returns recipient outcomes and an immutable event timeline. Message body content is not returned by that endpoint. New domains need three sending records: signing TXT (also domain ownership proof), bounce MX and SPF TXT. Existing domains keep their original verification records. Domain readiness requires the exact claim key in DNS plus signing, identity and return-path checks. Deliverability to an inbox is not guaranteed by domain verification.
Open and click tracking are off for every domain by default. Turn them on per domain with PATCH /domains/:id and { "open_tracking": true, "click_tracking": true } (a Manage project key). Opens add an invisible image and clicks send links through a redirect, which some inboxes treat as marketing, so keep tracking off for receipts and password resets and use it for newsletters, ideally from their own subdomain. Open and click events appear in an email's timeline and in analytics only for tracked domains. tracking_available on a domain says whether this server supports tracking yet.
Read recipient outcomes
Use the message's recipient records and event timeline to distinguish partial success from failure. A submitted message is accepted by the sending provider; delivered requires a provider delivery event. deferred indicates a temporary delivery issue. bounced, complained, failed and cancelled describe different terminal outcomes; use the timeline for the cause.
Signed webhooks let your app react to delivery changes without polling. Deduplicate events before updating your own records.
Suppressions
Suppressed recipients are blocked from sending. Suppressions and usage are shared across the account, while email resources stay in their project. A management key can inspect /v1/suppressions; review the underlying bounce or complaint before removing an entry. Removing a suppression does not establish recipient permission.
Warm-up and sending readiness
Sending opens when the account owner's email and a sending domain are verified, subject to account safeguards. A new domain warms up through batches that increase with clean sending. Paid plans have a monthly recipient quota without a plan-level daily limit; warm-up and reputation controls still pace delivery. See billing and limits.