Can one dedicated IP be mapped to multiple sub-domains for email?

Key findings

• Feasibility: A single dedicated IP can be associated with several subdomains for sending email.
• Flexibility: This setup allows for various organizational structures, particularly when email volume per subdomain is insufficient for individual dedicated IPs.
• Reputation sharing: All subdomains sharing an IP address contribute to and are affected by that IP's overall sending reputation.
• Warming requirements: Each new IP, even when linked to an already warmed-up domain, typically requires its own gradual warming period to establish a positive sending history with ISPs.

Key considerations

• Reputation risk: If one subdomain on a shared IP begins sending low-quality mail (e.g., spam), it can lead to the IP getting blocklisted or experiencing lower inbox placement for all associated subdomains. You can learn more about managing reputation with multiple IPs in our guide on how to manage subdomain reputation when using multiple IP addresses for email sending.
• Volume distribution: Ensure sufficient aggregate volume across all subdomains to justify a dedicated IP, as consistent sending volume helps maintain a good reputation.
• Segmentation: Carefully consider whether the email streams from different subdomains are compatible in terms of recipient engagement and content quality.
• Monitoring: Implement robust monitoring for all subdomains on the shared IP to quickly identify and address any deliverability issues. For insights on optimal setups, refer to our article on how many subdomains should I use per dedicated IP address for email sending.
• Dedicated IP usage: GoHighLevel support notes a domain can be linked to multiple IPs.

Key opinions

• Volume necessity: Marketers often highlight that dedicated IP per subdomain is ideal but not always feasible without high volume.
• Reputation ripple effect: A common concern is that a single problematic subdomain on a shared IP can harm the reputation for all other subdomains.
• Shared pool commonality: The existence of shared IP pools at email service providers (ESPs) indicates that sharing IPs is a practical solution for many senders.
• Careful stream management: Marketers recommend strong segmentation to protect the IP reputation when different email types or qualities share an IP.

Key considerations

• Email stream quality: If you have a subdomain for less desirable streams, it can negatively impact the IP reputation, directly affecting other streams. Consider how changing subdomain IP to main domain IP will impact deliverability.
• Cost versus benefit: Evaluate if the potential deliverability risks of sharing an IP outweigh the cost savings of not acquiring additional dedicated IPs.
• Monitoring engagement: Closely monitor engagement metrics for each subdomain to detect early signs of deliverability issues, especially if you use subdomains for promotional and transactional emails on a shared IP.
• Custom IP decision: Inbox Collective discusses whether a custom IP helps deliverability.

Key opinions

• Flexible mapping: Experts confirm that you can send mail from multiple 821.From domains off a single IP, and also use multiple IPs for a single 821.From domain.
• HELO integrity: It's critical not to interfere with the server's HELO command when configuring these setups.
• IP warming principle: A new IP, even when mapped to a well-reputed domain, requires its own warming-up process to establish its sender reputation with recipient ISPs.
• ISP variations: Experts note that some ISPs might benefit from an existing good domain reputation, while others will treat each new IP stream independently during warming.
• Baseline assumption: A conservative approach involves warming up each unique IP/authenticated-domain pair separately to ensure optimal deliverability.

Key considerations

• Reputation isolation: If you have varied email streams, consider segmenting them to different IPs to prevent a low-quality stream from damaging the reputation of a high-quality one. For more, see our page on how to manage subdomain reputation when using multiple IP addresses for email sending.
• Gradual ramp-up: Always ramp up traffic gradually on new IPs, even if they're associated with an established domain.
• Domain versus IP warm-up: Customer Engagement Blog highlights understanding domain versus IP warm-up.
• Domain authentication: Ensure proper SPF, DKIM, and DMARC authentication for all subdomains and IPs to verify sender identity and build trust. You might also want to review whether a dedicated IP address can be configured to identify email as transactional.
• Consistency: Consistent email volume and sending practices are vital for maintaining a healthy IP and domain reputation.

Key findings

• DNS configuration: DNS allows for multiple subdomains to point to the same IP address using A records, facilitating shared IP usage.
• Flexible IP assignment: Platforms like SendGrid allow assigning authenticated domains and dedicated IPs to subusers, demonstrating the ability to link domains to specific IPs.
• Server capacity: Dedicated servers and VPS typically support hosting multiple domains and subdomains on a single IP, limited only by server resources.
• Multi-homing: Multiple subdomains can point to the same IP, with different services potentially using different ports on that IP.

Key considerations

• Authentication records: Proper configuration of SPF, DKIM, and DMARC records is crucial for each sending domain, even when sharing an IP. For more details, check out whether sending domains should resolve to the same IP addresses as mail servers.
• Domain reputation management: Documentation often stresses the need to protect your sending domain's reputation, especially when multiple subdomains or IP addresses are involved.
• Traffic routing: While technically possible, documentation might advise on the implications of routing different subdomains to the same IP for email, particularly if they have vastly different content or recipient engagement. You might also want to read is it possible to point one subdomain to multiple email service providers?
• Dedicated IP capacity: Liquid Web documentation states dedicated servers can have multiple IP addresses.
• Subuser assignments: SendGrid's documentation outlines how to assign verified domains to subusers.