Domain Reputation and IP Reputation both affect deliverability and factor into the decisions email providers make on where to place the emails you send. Over time, however, domain reputation has become the dominant signal for many major mailbox providers, especially for B2B senders.
Mailbox providers like Gmail now prioritize domain signals over IP, because domains are harder to swap than IPs, and more tightly tied to brand identity. In this article, you will find clear definitions of IP and domain reputation, why domain-level signals matter more now, how to measure each, when a dedicated IP makes sense, and which practical fixes truly influence inbox placement.
TL;DR: Domain reputation and IP reputation are distinct deliverability signals, but modern mailbox providers like Gmail and Microsoft now overwhelmingly prioritize domain reputation (your brand's persistent "credit score") over IP reputation (the server's temporary history). While a clean IP address acts as an initial gatekeeper to prevent immediate blocking, it is your domain reputation—built on long-term engagement, authentication alignment (SPF/DKIM/DMARC), and rigorous list hygiene—that ultimately determines if a message lands in the primary inbox or the spam folder. Consequently, B2B senders should focus less on the "dedicated vs. shared IP" debate and more on using safety layers like Allegrow to remove spam traps and resolve catch-all addresses, ensuring their domain builds positive history with every send.
What is IP reputation, and how does it differ from domain reputation?
IP reputation is basically the trust assigned to the server or mail-sending IP address from which your emails are sent. The sending IP associated with your emails will look something like this ‘127.0.0.1’ (4 sets of numerals separated by periods). When a message arrives at a recipient server, the receiving mailbox provider first sees the sending IP. If that IP has a clean history, low bounce/complaint rates, and no signs of abuse, the connection stands a better chance of being accepted for further evaluation.
By contrast, domain reputation is tied to the domain in your “From:” address (Your email domain is whatever comes after the @ symbol in the email – so for us, that’s usually ‘allegrow.co’). It is brand-linked, persistent across different sending servers, and reflects long-term behavior. That is, how many messages you’ve sent, how recipients engage (opens, replies, complaints), whether your authentication is correct (SPF, DKIM, DMARC), how often your domain has been involved in spam-trap hits or other issues, and how clean and active your contact lists are. As a result, domain reputation travels with you, even if you switch ESPs or IPs.
You can think of domain reputation as forming a ‘credit score’ for your email domain. If people regularly; respond to, mark your messages as important and rarely mark them as spam – you’ll have a good credit score, and your emails are likely to land in the primary inbox. Whereas if more recipients ignore emails from your domain, rarely open them and don’t usually reply to them – you’ll have a low score, and email providers draw the conclusion they’d be doing their users a favor by filtering your message out of sight and into the spam folder.
Because IPs can be shared, recycled, or change hands, their history can be noisy or volatile, which caused email providers to move away from using data on IPs as the main way they make general filtering decisions. Domains, on the other hand, tend to provide a more stable, brand-specific signal of trust. As one analysis puts it, while IP reputation still serves as a first gate, domain reputation increasingly determines where your mail ends up: inbox, promotions, or spam. In fact, even SendGrid who is one of the largest providers of dedicated IPs, has noted that there has been a ‘sharp move towards domain reputation’ when ESPs are making filtering decisions.
Why are email providers prioritizing domain reputation?
Mailbox providers, especially major ones like Google (Gmail) and Microsoft (Outlook/Hotmail), increasingly prioritize domain-based signals for three main reasons.
First, domains are harder to swap out than IPs. It is trivial for a sender to change or rotate IPs, especially when using shared infrastructure, but the sending domain tends to remain constant over time. By focusing on domains, providers get a more stable, brand-specific reputation signal that reflects long-term behavior rather than ephemeral server changes.
Second, shared or dynamic IPs, which are common among many email service providers (ESPs), muddy attribution of bad behavior. If multiple senders share one IP, one spamming actor could drag down deliverability for others. That’s why domain history is a more precise data source, and domain-based evaluation avoids this “guilt by association” problem inherent to shared IPs.
Third, engagement and complaint signals are inherently tied to the recipient’s perception of the brand and domain, not the underlying sending server. When recipients open, reply, or mark mail as “not spam", they evaluate the visible “From:” address - that is, the domain, not the IP. Thus, mailbox providers view domain-level reputation as a more accurate representation of trust, authenticity, and sender identity. Many recent analyses and deliverability experts now consider domain reputation the primary driver for inbox placement for established senders.
Gmail in particular is widely documented as a domain-first filtering system, though IP reputation is still monitored for safety limits. Other providers like Microsoft and Yahoo follow a similar trend. That said, IP reputation is not obsolete. A poor IP, especially one flagged or blacklisted, can still override a solid domain reputation and block delivery entirely.
How reputation is built (inputs you actually control)
You cannot rely on luck when it comes to reputation. You control the levers that shape both domain and IP reputation over time. That’s because your domain reputation grows from a mix of engagement, list quality, and infrastructure hygiene.
The quality of your mailing list is paramount. That’s because high-quality lists reduce bounce rate, spam traps, and risky role accounts. Allegrow’s Safety Net verification helps you here by classifying catch-all domains as “valid” or “invalid” instead of “unknown”, surfacing spam traps, spam reporters, disposable addresses, and inactive mailboxes. This ensures new sends go to contacts that can actually improve reputation instead of harming it.
Consistency also matters, and you can minimize complaint rates by setting expectations, personalizing outreach, and pacing sends. Sending volume should ramp up gradually because sudden spikes, irregular frequency, or changes in volume can lower trust.
Additionally, authentication alignment through SPF, DKIM, and DMARC is essential because providers use aligned authentication to confirm identity and prevent impersonation. Alignment is required for Yahoo and Google’s sender guidelines. Without authentication alignment, even a well-maintained list can trigger suspicion, especially from providers that now make domain authentication a baseline requirement.
Audience fit also plays a role because highly relevant messaging is more likely to receive replies and positive engagement, which boosts domain reputation over time. Emails should provide value to recipients. Poorly targeted content or irrelevant messaging leads to low engagement, unsubscribes, or complaints - all negative signals for domain reputation.
Finally, monitoring and remediation are part of the process. If bounces or complaints rise, act immediately. Remove uninterested recipients, update suppression lists, and avoid “spray and pray” tactics.
How to track and measure domain and IP reputation
Modern sender reputation cannot be tracked from a single source. A robust tool stack helps you stay informed about your reputation health, and you need a mix of provider consoles, IP health checks, and inbox placement monitoring.
Gmail Postmaster Tools and other provider consoles
If you send to Gmail or other large inbox providers, use their official monitoring dashboards. For example, Gmail’s Postmaster Tools show domain and IP reputation tiers, spam-complaint rate, authentication pass/fail rates, encryption usage, and delivery errors. Microsoft and Yahoo offer smaller sets of data but follow a similar logic.
Reviewing these trends before major sends is critical. That way, you can detect degradation early and pause or adjust your sending accordingly. However, make sure to look for trends rather than single-day anomalies because reputation is calculated over time.
Blocklist lookups and IP health checks
Blocklist lookups provide information on whether an IP has been flagged by independent security organizations. Even though Gmail, Microsoft, and Apple do not rely heavily on most third-party blacklists, they still matter in certain cases, such as transactional systems or high-volume SMTP providers.
It is useful to treat blocklist lookups as an early warning signal rather than a definitive indicator. A quick check can reveal obvious issues, but many blocklists are outdated, have limited influence, or list shared IP ranges that rotate frequently. That’s why blocklist information should be interpreted cautiously, since many listings have little real influence on inboxing and may attempt to charge for removal.
Placement testing and KPI trending
Inbox placement testing is the only way to determine where your emails actually land. Allegrow monitors this daily, measuring primary inbox, promotions, and spam placement, then storing the results for long-term trend analysis.
You should also monitor internal KPIs such as bounce rate, spam complaint rate, reply rates, and click engagement. Shifts in these signals can indicate changes in reputation and should be reviewed after infrastructure changes, new messaging, or list imports.
Which one is better for domain reputation: Dedicated or shared IPs?
Whether you use a shared or dedicated IP matters less than many believe - unless you send at a very high, stable volume, and have strong operational discipline. Shared IPs often work perfectly for SMB senders who have relatively low to moderate volume, clean lists, and good domain practices. Shared infrastructures can benefit from pooling reputation across many senders, and shared IP health is managed by the provider.
A dedicated IP makes sense when you consistently send large volumes (tens or hundreds of thousands per month), when you want full control over warming, throttling, speed, and reputational isolation, or when you operate in sectors with strict compliance or deliverability requirements (such as transactional SaaS, finance, regulatory communications). However, it also means every mistake reflects directly on your IP, which increases risk for senders without tight sending operations.
Using a dedicated IP carries trade-offs: you need to warm it up carefully, avoid sudden spikes, maintain authentication records, monitor blocklists, and avoid mistakes - otherwise IP-level setbacks become your problem alone. Since filtering is now weighted toward domain reputation, a dedicated IP offers limited benefit unless you send very large volumes at predictable intervals.
Summary and next steps
Domain reputation and IP reputation both influence inbox placement, but domain signals carry the most weight in today’s filtering systems. They reflect the engagement patterns of real users and offer providers a more accurate way to predict sender trustworthiness.
A practical routine for maintaining domain health includes reviewing Gmail Postmaster Tools monthly, monitoring key KPIs, verifying lists, checking authentication alignment, and periodically reviewing inbox placement. After making meaningful changes such as new copy, list segments, or infrastructure updates, run small controlled tests and watch for placement shifts before scaling volume.
If you want to go beyond manual checks, use a tool that automatically tracks and alerts you about deliverability risk. That’s where Allegrow comes in: with our Safety Net verification, you can routinely vet contact lists, spot spam traps and risky addresses, identify valid contacts inside catch-all domains, and maintain clean sending practices - all crucial to keeping your domain and IP reputation intact as you grow.
If you manage lists of any size and send email regularly, we strongly recommend trying our 14-Day Free Trial. Upload up to 1,000 contacts, let Allegrow scan for traps and risky addresses, and get a clean, risk-scored list before your next campaign. This protects your domain reputation, reduces bounce and complaint risk, and ensures you start scaling from a clean baseline.
FAQs
Does a dedicated IP improve inboxing on its own?
A dedicated IP does not automatically improve inbox placement. Even though it gives you control over sending infrastructure, without clean lists, proper authentication, and regular engagement, a dedicated IP alone does little. In fact, a poorly warmed or misused IP can harm deliverability more than a stable shared IP linked to a well-maintained domain. For most B2B teams, domain reputation is the primary lever for inboxing.
Why does Gmail sometimes rate my domain ‘low’ but my IP ‘medium’?
Domain reputation reflects engagement and complaints specific to your organization, while IP reputation reflects the behavior of the server or range. A medium IP rating means the sending server is healthy, but a low domain rating indicates that mailbox providers have observed poor engagement, complaints, or other issues tied to your domain’s history. Since domain reputation increasingly drives final inbox placement, you’ll likely still face deliverability problems unless domain issues are addressed.
Do subdomains have separate reputations from the root domain?
Subdomains maintain their own reputation profiles, but providers still consider the interconnected history of the root domain. Using different subdomains for different mailing streams allows you to isolate reputational risk, but it does not erase poor domain history. This technique is often used to protect critical streams like transactional email while maintaining aggressive marketing outreach elsewhere.
Should I change IPs if my inbox placement drops suddenly?
Changing IPs can sometimes provide temporary relief, especially if the old IP was blacklisted or strongly damaged. But without fixing underlying issues - such as list hygiene, engagement, authentication, or spam-trap exposure - you risk regenerating the same problem on the new IP. Because domain reputation travels with you across IPs, it’s often more effective to focus on domain-level fixes before switching infrastructure.
How can you check your IP reputation and spot blacklist issues?
You can run IP checks through blocklist lookup tools, but keep in mind that many blocklists are less relevant for large mailbox providers like Gmail or Outlook. Blacklisting may matter more for smaller enterprise domains or strict transactional receivers. Your email service provider may also provide IP health visibility if you use a dedicated or semi-dedicated environment.
