How to handle domain cross-contamination between brands?

Domain cross-contamination occurs when reputation problems spread between related brands sharing infrastructure, parent domains, or authentication records. Prevention requires deliberate isolation.

Use completely separate root domains for distinct brands rather than subdomains under a shared parent. Each brand should have independent SPF, DKIM, and DMARC configurations. Consider separate IP pools if volumes justify dedicated infrastructure.

Avoid sharing sending accounts, ESP platforms, or link tracking domains across brands if reputation isolation is critical. Each shared element creates a potential contamination pathway.

Cross-contamination is like a disease spreading between ships docked in the same harbor. The only reliable prevention is keeping the vessels in separate ports entirely, with no shared crew or supplies.