Using multiple subdomains on a single dedicated IP address for different email types (e.g., transactional and marketing) is a generally recommended strategy for improved email deliverability and sender reputation management. Subdomains enable segmentation of email traffic, allowing for the building of independent reputations and isolation of deliverability issues. To further separate treatment of mail streams, different DKIM signatures can be used, and different SPF records provide flexibility in authentication. While subdomains offer benefits, the IP address's overall reputation remains key. Careful monitoring of both the IP address and each subdomain's performance is crucial, as poor performance on one subdomain can negatively affect the entire IP's reputation. Low sending volumes may extend subdomain warmup periods, and it is important that ALL subdomains are compliant or it may impact your deliverability.