Best of the inbox: structuring sending subdomains

Best of the inbox: structuring sending subdomains
Mixing mail streams on one domain means one bad campaign poisons all of them. Here's the separation map.

🏗 Architecture
— Split by reputation risk, not by team — transactional, marketing, and re-engagement each get their own subdomain. Isolate the risky from the critical.
— Keep transactional on its cleanest subdomain — receipts and resets must never share reputation with promo blasts.

🔧 Setup
— Separate DKIM keys per subdomain — so a problem on one doesn't cross-contaminate alignment on another.
— Warm each independently — a new subdomain is cold even if the root domain is established.

🛡 Govern
— Document which stream lives where — future-you and your ESP migration will thank you.

Why these picks: risk-based isolation is the architecture deliverability pros use, and most senders never set it up.

Saved you ~2 hours of structure research.