Experts and marketers generally advise against using the same domain for both cold outreach and regular email due to the risk of shared reputation, potentially leading to delivery and blocking problems. Using a subdomain can isolate reputation issues, but subdomains are still tied to the main domain, so a poor reputation in one can affect the other. It is crucial to protect sending reputation by segregating cold outreach to separate domains or subdomains. Proper email authentication (SPF, DKIM, DMARC) is essential to prevent spoofing and improve deliverability. Furthermore, even when using different domains or subdomains, using the same IPs can negatively impact IP reputation, and proper email warm-up is vital for any domain used for outreach.