Using subdomains for different email types is a common and recommended practice to isolate sender reputation and prevent deliverability issues of one email type from negatively impacting others. While subdomains offer some independence, search engines and mailbox providers can still connect them to the main domain. Key to successful implementation includes properly configuring email authentication (SPF, DKIM, DMARC) for each subdomain, regularly monitoring subdomain reputation for blocklisting, and maintaining separate IP addresses. Recipient engagement and avoiding unsolicited emails are also critical factors in ensuring positive sender reputation. The overall impact depends on the details, setup, usage, and consistent management of the subdomains.