postmarklisted

# Postmark Postmark sends transactional email over an authenticated SMTP relay or HTTP API, and exposes delivery status through the same API — use it whenever a system needs outbound email that must actually land in the inbox rather than direct-from-origin SMTP, which unauthenticated senders (residential IPs, ad hoc hostnames with no SPF/DKIM) get spam-filtered on almost immediately. ## Message streams — pick the right one Every Postmark server has (at minimum) three message streams, visible under Servers → *server name* → Message Streams: | Stream | Stream ID | Use for | |---|---|---| | Default Transactional Stream | `outbound` | One-to-one, system- or app-generated email: alerts, receipts, password resets, backup/job notifications. **Default choice for almost everything.** | | Default Broadcast Stream | (custom ID) | Bulk/marketing sends to many recipients at once. Requires unsubscribe handling. Never use for system notifications. | | Default Inbound Stream | `inbound` | Receiving mail routed to Postmark, not sending. Irrelevant for sending tasks. | Note the Transactional stream's actual ID is literally `outbound` despite the UI label "Transactional" — this shows up in API responses (`"MessageStream": "outbound"`) and is correct, not a sign something is misconfigured. ## Prerequisite: verified sender Postmark rejects any send whose `From` address isn't a verified Sender Signature (single address) or a verified Domain in that account. Before configuring anything, conf