> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stackra.figentra.com/llms.txt
> Use this file to discover all available pages before exploring further.

# 0191 — Email deliverability

> Accepted · 2026-10-20

> [!NOTE]
>
> Supersedes [0035](/adr/0035-resend-email-with-spf-dkim-dmarc). The SPF, DKIM and DMARC steps of
> 0035 (decisions 1 to 3) carry forward.

## Context

[0035](/adr/0035-resend-email-with-spf-dkim-dmarc) (Proposed) chose Resend with the mail-authentication records. The owner's answer PP9 (mem L562, 2026-10-20) adds subdomains per environment, separate streams, a DMARC ramp, custom sending domains for tenants, and an SMTP relay on-prem.

## Decision

1. **Subdomains.** Email is sent from a subdomain per environment.
2. **Streams.** Transactional and marketing mail use separate streams.
3. **DMARC ramp.** DMARC policy ramps to `reject`.
4. **Tenant sending domains.** Tenants can use their own sending domain. This is a Pro entitlement (ADR 0242).
5. **On-prem.** An SMTP relay is used, behind the same mail driver.
6. **Provider.** Resend sits behind the mail driver, so the provider can change.

## Consequences

* A marketing problem cannot damage transactional delivery, because the streams are separate.
* A tenant sending domain is a plan feature, not a code path.

## Enforcement

planned — the DNS records are checked by the infrastructure stack (ADR 0171); the mail driver's contract test covers the SMTP relay.

## Alternatives

* One stream for all mail: rejected; a marketing complaint would affect password resets.

## Supersedes and sources

Supersedes: [0035](/adr/0035-resend-email-with-spf-dkim-dmarc). Sources: owner answer PP9 (`stackra-decisions-2026-10-19.md` L562, 2026-10-20). Closes gap C39.


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