What are the implications of sharing a dedicated IP address for multiple domains within the same company?
Matthew Whittaker
Co-founder & CTO, Suped
Published 23 Jul 2025
Updated 19 Aug 2025
8 min read
When managing email infrastructure for a company with multiple divisions or brands, a common question arises: what are the implications of sharing a dedicated IP address across these distinct domains? While a dedicated IP offers control over your sending reputation, consolidating multiple domains on one such IP, even within the same organization, introduces unique considerations for email deliverability. It's a strategic decision that balances efficiency with potential risks to your sender reputation.
The primary concern centers around how internet service providers (ISPs) and mailbox providers perceive and evaluate your sending behavior when multiple domains originate from the same IP. While technically possible and often done, understanding the nuances of IP and domain reputation is crucial to maintain high inbox placement rates. We'll explore the various factors at play and how to mitigate potential downsides.
Navigating email reputation with a shared dedicated IP
Understanding how email reputation is assessed is fundamental when multiple domains share a dedicated IP address. Both your IP address and your domain have their own reputations, which ISPs use to determine if your emails should reach the inbox or be flagged as spam.
IP reputation and domain reputation
When you share a dedicated IP across several domains, the IP's reputation becomes a shared asset and liability. If one domain exhibits poor sending practices, such as high bounce rates, low engagement, or spam complaints, it can negatively impact the shared IP's reputation. This, in turn, can affect the deliverability of emails sent from all other domains on that same IP, even if those domains maintain excellent sending hygiene.
However, domain reputation provides a layer of distinction. Providers like Gmail and Microsoft also track reputation at the domain level. This means that even if the shared IP suffers a minor dip in reputation, a strong, positive domain reputation can help mitigate the impact for that specific domain. It's a critical factor that can help keep your metrics distinct. Learn more about managing your subdomain reputation when using multiple IPs.
Deliverability and blocklist implications
The shared nature of the dedicated IP means that deliverability challenges or triumphs for one domain will inevitably influence the others. This is particularly true concerning email blocklists (or blacklists), which are lists of IP addresses or domains with poor sending reputations. If one of your domains gets the shared IP blocklisted, all domains sending from that IP will experience delivery issues.
Blocklist risks and mitigation
When your dedicated IP is shared among multiple domains within your company, a single instance of poor sending behavior, such as sending to a large number of inactive addresses or generating high spam complaints from one domain, can lead to the shared IP being placed on a blocklist. This means emails from all your company's domains sharing that IP could be rejected or sent to spam folders, regardless of their individual sending practices. Understanding what happens when your IP gets blocklisted is essential.
To mitigate this, stringent monitoring and consistent sending practices across all domains are critical. Each domain should adhere to best practices for list hygiene, content quality, and recipient engagement. This collective responsibility is key to maintaining a healthy shared IP reputation. You can also explore when to use a shared IP address instead of dedicated if these risks are too high.
Shared warming: A new domain sharing an IP will benefit from the existing reputation of the IP, which can accelerate its warm-up period. Conversely, a poor-performing domain can quickly damage a well-established IP.
Engagement feedback loops: ISPs monitor engagement metrics (opens, clicks, complaints). If one domain sees a sudden spike in complaints, it signals problematic behavior associated with the shared IP.
List quality: Each domain must maintain clean and engaged mailing lists. High rates of unknown users or spam traps from any domain will harm the shared IP.
Technical considerations and email authentication
From a technical standpoint, sharing a dedicated IP for multiple domains within the same company generally doesn't pose significant issues for email authentication protocols like SPF, DKIM, and DMARC. These protocols primarily rely on domain-level configurations.
SPF, DKIM, and DMARC
For SPF (Sender Policy Framework), each domain will need its own SPF record, specifying the shared dedicated IP as an authorized sender. This record is published in the domain's DNS. Similarly, DKIM (DomainKeys Identified Mail) keys and records are configured per domain or subdomain. The private key used to sign the email is associated with a specific domain, and the public key is published in that domain's DNS.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) policies are also set at the domain level. Each domain will have its own DMARC record, dictating how mailbox providers should handle emails that fail SPF or DKIM authentication, and where to send reports. The shared IP itself doesn't typically complicate these setups, as long as each domain correctly implements its own authentication records. For more on this, consult a simple guide to DMARC, SPF, and DKIM.
The key is ensuring that each domain's DNS records are properly configured to reflect the shared IP and the email sending platform being used. This includes making sure any email service provider (ESP) includes for SPF are present, and that DKIM selectors are correctly mapped.
Proactive management for deliverability success
While sharing a dedicated IP within the same company can be advantageous for internal consistency and cost, it requires diligent management to prevent negative impacts on deliverability. Proactive monitoring and adherence to best practices are essential.
Monitoring and consistent practices
One of the most effective strategies is to implement robust monitoring for all domains sharing the IP. This includes tracking IP and domain reputation through tools like various postmaster tools (e.g., Google Postmaster Tools) and blocklist monitoring services that track numerous blocklists. Early detection of any reputation issues on one domain allows for swift remediation, protecting the collective IP reputation. Regular audits of sending practices for each domain are also crucial to ensure compliance with email sending guidelines.
Consistency in email volume and sending patterns across all domains can also help. ISPs prefer steady, predictable sending behavior. Erratic sending from one domain, even if temporary, can raise flags for the entire IP. Ensuring all domains implement strong authentication, such as DMARC with a enforcement policy, further reinforces sender legitimacy and helps mailbox providers correctly identify and deliver your emails. This proactive stance is key to avoiding issues and maximizing email deliverability across your company's brands.
Achieving deliverability success with shared dedicated IPs
Sharing a dedicated IP address across multiple domains within the same company is a common practice, and it can be highly effective when managed correctly. The key takeaway is that while the IP reputation is shared, individual domain reputations provide a crucial layer of distinction and protection. As long as all domains maintain strong sending hygiene and consistent practices, the setup should not lead to significant deliverability issues.
However, the shared nature of the IP means that any misstep by one domain can potentially impact all others. Vigilant monitoring of IP and domain reputation, adherence to email authentication best practices, and proactive management of sender behavior are paramount. With careful attention, a shared dedicated IP can be a reliable foundation for your company's email programs across multiple brands.
Views from the trenches
Best practices
Maintain consistent and high-quality sending practices across all domains sharing the IP, focusing on list hygiene and engagement.
Utilize Postmaster Tools from major mailbox providers to monitor IP and domain reputation metrics regularly.
Ensure proper implementation of SPF, DKIM, and DMARC for each domain, with individual domain-level records.
Common pitfalls
Ignoring poor sending performance from one domain, which can quickly degrade the shared IP's overall reputation.
Failing to monitor blocklists, leading to delayed detection and prolonged deliverability issues for all domains.
Inconsistent email volume or sudden spikes from one domain can negatively affect the shared IP's trust with ISPs.
Expert tips
For companies with very different sending profiles or recipient bases across domains, consider separate dedicated IPs for high-risk or high-volume sending streams.
Implement a centralized dashboard for reputation monitoring to get a holistic view of all domains sharing the IP.
Establish clear internal guidelines for email sending practices for all teams and departments using the shared IP.
Expert view
Expert from Email Geeks says that as long as IP and domain reputations are good, sharing a dedicated IP among multiple company domains has not been an issue in over 20 years for many certification customers, including entire ESPs.
2023-01-10 - Email Geeks
Expert view
Expert from Email Geeks says that you will share IP reputation between the brands, but this is much better than sharing an IP with unrelated companies, and the separate domain reputation will help keep metrics distinct at Gmail and Microsoft.
Gmail and 
Microsoft also track reputation at the domain level. This means that even if the shared IP suffers a minor dip in reputation, a strong, positive domain reputation can help mitigate the impact for that specific domain. It's a critical factor that can help keep your metrics distinct. Learn more about managing your subdomain reputation when using multiple IPs.
