How can I check if an email is sent from a dedicated or shared IP without contacting the ESP?
Michael Ko
Co-founder & CEO, Suped
Published 15 Jun 2025
Updated 17 Aug 2025
7 min read
Determining whether an email originates from a dedicated or shared IP address without direct confirmation from the Email Service Provider (ESP) is a common challenge for email marketers and deliverability professionals. While ESPs typically manage their IP allocations internally and don't always disclose specifics, there are several investigative methods you can use to deduce this information.
Many of us might start by analyzing the return-path domain in the email headers, assuming that if it belongs to the ESP, it indicates a shared IP. However, this assumption can be misleading because some ESPs offer clients the option to "white label" their return-path, meaning it can appear to be the sender's domain even if it's a shared IP. It truly doesn't definitively imply anything either way.
While there's no single foolproof method to know with 100% certainty, combining clues from email headers, reverse DNS lookups, and IP reputation data can provide strong indications. This approach allows for a more informed assessment of the IP type without needing to contact support.
Extracting the sending IP from email headers
The first step in this investigation is to examine the email headers, which contain a wealth of information about the message's journey. You'll want to find the "Received: from" lines, which log the servers that handled the email before it reached your inbox. The key is to identify the IP address of the last sending server that isn't your own mail server.
To access email headers, the process varies slightly depending on your email client. In Gmail, you can click the three dots next to the reply icon and select "Show original." For Outlook, it's usually under "File" > "Properties" > "Internet Headers." Once you have the full headers, locate the "Received: from" lines. The IP address you're looking for will often be associated with the last "Received: from" entry before your mail server, or within the "X-Sender-IP" or "X-Originating-IP" headers, if present.
Remember, the presence of an ESP's domain in the return-path, while a clue, doesn't definitively indicate a shared IP. It's crucial to understand how to determine an email sending platform from headers more broadly before drawing conclusions about IP types based solely on the return path.
Example email header snippetplain
Received: from mail-tester.com ([XX.XXX.XXX.XXX])
by your-mail-server.com with ESMTP id ABCDEFGHIJ
(version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO)
for <your-email@yourdomain.com>; Mon, 1 Jan 2024 12:00:00 +0000
Received: from [another-server.esp.com] (another-server.esp.com [YY.YYY.YYY.YYY])
by mail-tester.com (Postfix) with ESMTP id ZYXWVUTSRQ
for <your-email@yourdomain.com>; Mon, 1 Jan 2024 11:59:50 +0000
Reverse DNS and SPF records as indicators
Once you have the sending IP address, the next step is to perform a reverse DNS (rDNS) lookup. This checks the Pointer (PTR) record associated with the IP. If the rDNS record contains a name that clearly identifies the sender or their brand, it's a strong indicator that the IP is dedicated. For example, an rDNS like "mail.yourdomain.com" suggests a dedicated IP, whereas a generic one like "mta-outbound.espname.net" could be either a shared or dedicated IP.
Another clue lies in the sender's SPF (Sender Policy Framework) record. If the SPF record for the sending domain directly includes the specific sending IP address (e.g., via an "ip4:" or "ip6:" mechanism), it often points to a dedicated IP. Conversely, if the SPF record primarily includes the ESP's broad IP ranges or uses "include:" statements for the ESP's domain, it becomes less clear if it's a dedicated IP or part of a shared pool. Understanding how SPF, DKIM, and DMARC affect deliverability is essential here.
Limitations of DNS Indicators
While rDNS and SPF can offer strong hints, they are not always definitive. Many ESPs use IP ranges for both shared and dedicated customers that look very similar from the outside. Some ESPs also don't bother setting customer-specific rDNS for dedicated IPs, making it indistinguishable from a shared pool without internal knowledge. This makes it difficult to ascertain with absolute certainty without direct contact, highlighting the challenges in configuring reverse DNS for both shared and dedicated IPs effectively.
Leveraging IP reputation and blocklist (blacklist) data
IP reputation services can also provide valuable insights. Websites like Sender Score allow you to look up an IP address and see the number of domains associated with it and its sending history. If a large number of diverse domains are sending mail from that IP, it's a strong indicator of a shared IP address (or a shared blocklist/blacklist pool). Conversely, if very few or only related domains are sending from that IP, it suggests a dedicated IP. This is a common way to indirectly determine the IP type and its standing, as a healthy IP reputation is crucial for deliverability.
Another method is to use inbox placement tests or seed list services. If you have the ability to send emails through the ESP in question (e.g., if you're a client testing a new account setup), these services send your emails to a wide array of test mailboxes and report the sending IP addresses. If you consistently see the same IP address across multiple test sends, it likely indicates a dedicated IP. If you see a variety of IPs, it's almost certainly a shared pool. These tools also help in understanding how email blocklists function, as a single bad actor on a shared IP can affect everyone.
However, these reputation services, while helpful, still won't give you a definitive "shared vs. dedicated" label from the ESP itself. They provide empirical evidence of usage patterns. This data is invaluable for understanding which companies might be sharing your IP address if you are on a shared pool, but direct confirmation remains elusive without ESP contact. Understanding what being blacklisted means on a shared IP is also critical.
Dedicated versus shared IP considerations
At its core, a dedicated IP address is exclusively used by one sender, giving them complete control over their sending reputation. A shared IP address, on the other hand, is utilized by multiple senders, and its reputation is an aggregate of all users' sending practices. This distinction is critical for your email deliverability, as a single sender's poor habits on a shared IP can negatively impact your own email performance.
Dedicated IP
Control: You have full control over your IP's reputation. Your deliverability is solely dependent on your own sending practices.
Reputation building: Requires a dedicated IP warmup process to build trust with ISPs, especially for high-volume senders.
Volume: Ideal for senders with consistent, high email volumes who can maintain a good reputation.
Cost: Typically comes at an additional cost from your ESP.
Shared IP
Control: Less control over reputation, as it's influenced by all users on the IP pool. Risk of being blacklisted due to others.
Reputation building: ESP manages warming. Beneficial for new senders or those with low/inconsistent volumes.
Volume: Suitable for low-volume or irregular senders, as the collective volume helps maintain reputation.
Cost: Usually included in basic ESP packages.
Understanding which type of IP an email is sent from can inform your own sending strategy and help you better diagnose deliverability issues. For example, if you consistently see a shared IP associated with a sender experiencing deliverability problems, it might suggest the need to consider a dedicated IP if their sending volume justifies it. More information is available on when to use a shared or dedicated IP.
Views from the trenches
Best practices
Always analyze multiple emails from the same sender over time; a single email might not be representative.
Compare the IP's rDNS with known patterns of major ESPs; generic names often suggest shared pools.
Common pitfalls
Relying solely on the Return-Path domain; it can be white-labeled even for shared IPs.
Assuming a generic rDNS always means a shared IP; some dedicated IPs might have generic rDNS set by ESPs.
Expert tips
Be aware that some ESPs use elastic IPs, which can make it hard to track consistent patterns.
Shared IP ranges from providers often change, making it a moving target for definitive identification.
Expert view
Expert from Email Geeks says you can get the IP address from the headers and check its reverse DNS; if it's customer-specific, it's likely dedicated, but if it's generic, it could be a pool.
2024-01-05 - Email Geeks
Marketer view
Marketer from Email Geeks says there isn't any definitive way to know if an IP is dedicated or shared without asking the ESP directly.
2024-01-06 - Email Geeks
Making an informed assessment
While definitively identifying whether an email is sent from a dedicated or shared IP without contacting the ESP remains a complex task, a combination of technical analysis and observation can provide strong indicators. By meticulously examining email headers for the sending IP, performing reverse DNS lookups, and cross-referencing with IP reputation services, you can gather sufficient evidence to make an educated assessment.
Remember that no single piece of information is foolproof, as ESPs often have intricate IP management strategies. However, by understanding these technical details, you empower yourself to better understand email flows and proactively address potential deliverability issues, whether on a dedicated or shared IP.
Gmail, you can click the three dots next to the reply icon and select "Show original." For 
Outlook, it's usually under "File" > "Properties" > "Internet Headers." Once you have the full headers, locate the "Received: from" lines. The IP address you're looking for will often be associated with the last "Received: from" entry before your mail server, or within the "X-Sender-IP" or "X-Originating-IP" headers, if present.
