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.

Using multiple subdomains on a single dedicated IP address for different email types (e.g., transactional and marketing) is a common and generally accepted strategy to improve email deliverability and manage sender reputation. By segmenting email traffic onto separate subdomains, senders can build independent reputations for each email type, isolate deliverability issues, and protect the main domain's reputation. However, it is crucial to monitor the reputation of both the IP address and each subdomain individually, as poor performance on one subdomain can affect the overall IP reputation. It allows for better management of bounces and unsubscribes for marketing purposes. If your subdomains do not meet best sending practices, it may impact your deliverability.

Experts agree that using subdomains on the same IP address is a good practice for segmenting mail streams and managing reputation. Separating transactional and marketing emails prevents the negative impact of marketing campaigns from affecting transactional deliverability. To encourage separate treatment of these mail streams, different DKIM signatures can be used. Additionally, different SPF records for each subdomain can provide flexibility in authenticating various mail streams. However, low sending volumes may result in a longer warmup period for the subdomains. Compliance across ALL subdomains is critical, as non-compliance will negatively impact deliverability.

Using subdomains to segment email streams can help to isolate issues and manage deliverability. While maintaining a good IP address reputation is key, dividing traffic into different subdomains facilitates better organization, tracking, and reputation management. Correctly setting up SPF records is also important to use multiple subdomains. Sending consistent email, having low bounce and complaints is important.