How can I check if an email is sent from a dedicated or shared IP without contacting the ESP?

Summary

Determining whether an email originates from a dedicated or shared IP without contacting the ESP involves a multi-faceted approach. First, extract the sending IP from the email headers (accessible via 'Show original' in Gmail or the 'Received' header). Then, conduct a reverse DNS lookup on the IP. A customer-specific domain suggests a dedicated IP, while a generic ESP name often indicates a shared IP. Analyze the sender's SPF and DKIM records: if the SPF includes the specific sending IP, it's likely dedicated; an ESP record hints at a shared IP. Utilize sender reputation tools (like Sender Score or Inbox Monster) to assess the IP's reputation and associated domains. Seed listing tools and inbox placement tests reveal the various IPs used. If trap hits from multiple domains appear, it may be a shared IP. However, bear in mind that many ESPs employ shared IP pools difficult to distinguish externally, and that you should also check the return-path email header and DNS records of the domain. Ultimately, external methods provide clues, but direct confirmation with the ESP remains the most reliable method.

Key findings

  • IP Extraction: The sending IP is found within the email headers.
  • Reverse DNS Clues: Customer-specific rDNS often suggests a dedicated IP, whereas generic ESP rDNS suggests shared.
  • SPF/DKIM Records as Indicators: SPF records including the sending IP indicate dedicated; including the ESP's range suggests shared.
  • Sender Reputation Analysis: Sender Score and similar tools reveal reputation and associated domains, assisting in identification.
  • Seedlist & Inbox Testing: Seed list testing and inbox placement tests show all sending IPs used.
  • Limits to External Analysis: Distinguishing dedicated vs. shared IPs externally can be challenging due to ESP configurations.

Key considerations

  • Reliability Concerns: External checks offer hints, but ESP confirmation remains the most reliable method.
  • Complexity of ESPs: ESPs commonly use shared IP pools difficult to differentiate from dedicated IPs.
  • Tool Combination: Combining multiple tools and techniques yields a more comprehensive assessment.
  • rDNS Nuances: Customer-specific rDNS offers better indication, yet any result needs further analysis.
  • Potential for False Positives: External analyses might lead to inaccurate determinations without ESP verification.
  • Return-Path Analysis: Don't forget to check return-path email headers and DNS records

What email marketers say
11Marketer opinions

To determine if an email originates from a dedicated or shared IP address without contacting the ESP, email marketers employ various methods. Analyzing email headers to extract the sending IP is a common starting point. Tools like MXToolbox, WhatIsMyIPAddress, and online reverse DNS lookup services can then be used to investigate the IP. Examining SPF and DKIM records can reveal if the IP is associated with a generic ESP range (suggesting a shared IP) or a specific entry (indicating a dedicated IP). Sender reputation tools, such as senderscore.org and Inbox Monster, can provide insights into the IP's reputation and the number of domains using it. Performing inbox placement tests and analyzing the IPs from which the emails arrive can also help differentiate between shared and dedicated IPs. IP lookup tools and seed list testing are other ways of identifing them. Ultimately, it's a process of gathering clues from various sources to make an informed assessment.

Key opinions

  • Header Analysis: Email headers reveal the sending IP address, crucial for further investigation.
  • Reverse DNS: Reverse DNS lookups can indicate if an IP is dedicated (customer-specific domain) or shared (generic ESP name).
  • SPF/DKIM Records: Examining SPF/DKIM records can highlight the number of domains sending email from the IP, giving clues about whether it is shared or dedicated.
  • Sender Reputation: Sender score tools provide reputation data and associated domains, helping to identify shared IPs.
  • Inbox Placement: Inbox placement tests expose the sending IPs, allowing for comparisons and identification of shared pools.

Key considerations

  • Tool Variety: A combination of tools and techniques provides a more comprehensive assessment than relying on a single method.
  • Accuracy Limitations: External methods may not always be definitive, and ESPs may obfuscate IP configurations.
  • Dynamic IPs: Some ESPs use dynamic IP ranges, making identification challenging over time.
  • Reputation Impact: Shared IPs can impact sender reputation due to the actions of other users on the same IP.
  • Probing Methods: Be aware that extensive probing of IP addresses may violate terms of service or trigger security alerts.
Marketer view

Email marketer from Mailjet explains that you can check the SPF record of the sending domain. If the SPF record includes the ESP's general IP ranges, it's likely a shared IP. A dedicated IP might have a specific entry.

December 2024 - Mailjet
Marketer view

Email marketer from Email Geeks explains that most seedlisting tools involve a large number of target mailboxes, and they will show in the report all the various IPs and their PTR records that the messages came from, and this can be used to identify if an IP is shared or dedicated.

June 2023 - Email Geeks
Marketer view

Email marketer from MailchimpCommunity.com shares to use inbox placement tests. Review report to see all the IPs that the messages came from.

September 2023 - MailchimpCommunity.com
Marketer view

Email marketer from WarriorForum.com shares that you can use IP lookup tools to do a lookup of the IP address, they will tell you who owns the IP - if its a generic IP or one owned by the company.

September 2023 - WarriorForum.com
Marketer view

Email marketer from Reddit user u/EmailExpert shares that you can use online tools like MXToolbox or WhatIsMyIPAddress to check the IP address and perform reverse DNS lookups.

January 2024 - Reddit
Marketer view

Email marketer from Neil Patel explains that you can check the email headers to find the IP address the email was sent from.

July 2023 - Neil Patel
Marketer view

Email marketer from Email Geeks shares that in the past, with just the IP, they've used sender score to see if other domains use it. Now they use Inbox Monster’s History Search. If they see trap hits from multiple domains in the last 90 days it’s likely dedicated.

July 2023 - Email Geeks
Marketer view

Email marketer from EmailMarketingForum.com shares that use sender score websites to check reputation of an IP address. A shared IP will often show multiple domains sending email.

October 2023 - EmailMarketingForum.com
Marketer view

Email marketer from stackoverflow.com shares to check SPF and DKIM records to see how many domains are sending email from the IP

January 2022 - Stackoverflow.com
Marketer view

Email marketer from Email Geeks shares that you can look up the IPs on senderscore.org and if you see lots of domains sending, it's shared.

December 2024 - Email Geeks
Marketer view

Email marketer from Website Law and Strategy shares that you can use sender reputation monitoring tools to see what IPs are related to the domain you are testing.

September 2023 - Website Law and Strategy

What the experts say
5Expert opinions

Determining if an email is sent from a dedicated or shared IP without contacting the ESP involves examining email headers, reverse DNS, and SPF records. Checking if the IP resolves to a generic ESP name (shared) or a customer-specific domain (dedicated) is crucial. If the sender's SPF record includes the sending IP, it suggests a dedicated IP; including the ESP record might indicate a shared IP. Reverse DNS that is customer-specific suggests dedicated IPs, but if not, it is uncertain. Ultimately, external determination can be difficult because many ESPs use shared IP pools indistinguishable from dedicated IPs from the outside, making direct inquiry to the ESP the most reliable method.

Key opinions

  • Header Analysis: Email headers provide the sending IP address.
  • Reverse DNS: Customer-specific reverse DNS often indicates a dedicated IP; generic reverse DNS may signify a shared IP.
  • SPF Record: If the sender's SPF record includes the sending IP, it's more likely dedicated; including the ESP's record could mean a shared IP.
  • External Limits: External methods often cannot definitively determine shared vs. dedicated IPs due to ESP configurations.

Key considerations

  • Reliability: External methods provide hints but aren't always accurate; confirming with the ESP is the most reliable approach.
  • Shared IP Pools: Many ESPs use shared IP pools that are difficult to distinguish from dedicated IPs externally.
  • Customer-Specific rDNS: If reverse DNS is customer-specific, it is more likely a dedicated IP; otherwise, the result is uncertain.
  • ESP Configurations: ESPs may intentionally obscure IP configurations, making external identification challenging.
Expert view

Expert from Email Geeks shares that they asked an ESP if there was a way to tell their dedicated IPs from pools from the outside, and the ESP said no. If there is a customer-specific rDNS, that is dedicated, but if there's not, it's anyone's guess.

September 2021 - Email Geeks
Expert view

Expert from Spam Resource, John Levine, explains that you can check the IP information to see if the IP resolves to a generic ESP name (likely shared) or to a customer-specific domain (likely dedicated). He also mentions that reverse DNS (rDNS) should point to the sending domain for dedicated IPs.

April 2021 - Spam Resource
Expert view

Expert from Email Geeks explains that if the sender's SPF record has the sending IP in it, it's dedicated. If it's including the ESP record, it might be a pool.

November 2022 - Email Geeks
Expert view

Expert from Email Geeks shares that you can get the IP address from the headers and check the reverse DNS. If it looks customer-specific, it's dedicated. If it looks generic, it might be a pool.

April 2023 - Email Geeks
Expert view

Expert from Word to the Wise, Laura Atkins, responds that accurately determining shared vs. dedicated IPs from the outside is often impossible. While reverse DNS can be a hint (customer-specific is more likely dedicated), many ESPs use shared IP pools that are difficult to distinguish. She also emphasizes asking the ESP is the most reliable method.

March 2024 - Word to the Wise

What the documentation says
5Technical articles

Determining the origin of an email (dedicated or shared IP) involves extracting the IP address from the email headers (viewable via 'Show original' in Gmail or examining the 'Received' header) and then performing a reverse DNS lookup on that IP. The return-path email header can also be examined and the DNS records of the domain checked. If the resulting hostname includes the sender's domain, it's more likely a dedicated IP. Resources like DigitalOcean provide guidance on how to perform and interpret reverse DNS queries.

Key findings

  • Header Extraction: Email headers contain the sending IP address.
  • Reverse DNS Lookup: Reverse DNS queries reveal the hostname associated with the IP address.
  • Hostname Interpretation: Dedicated IPs often have hostnames that include the sender's domain.
  • Return-Path Analysis: Checking return-path email header and DNS records of the domain

Key considerations

  • Header Location: The method for viewing email headers varies depending on the email provider (e.g., Gmail).
  • Reverse DNS Reliability: Reverse DNS results may not always be conclusive and can be configured differently by ESPs.
  • Shared IP Complexity: Shared IPs may not have a clear correlation between the hostname and the sending domain.
  • Technical Expertise: Performing reverse DNS queries and interpreting the results requires some technical knowledge.
Technical article

Documentation from SparkPost explains that you can perform a reverse DNS lookup on the IP address found in the email headers to determine if the IP is dedicated or shared. A dedicated IP will typically have a hostname that includes the sender's domain.

August 2024 - SparkPost
Technical article

Documentation from Microsoft shares to look for the 'Received' header which will reveal the IP that the email was sent from.

August 2021 - Microsoft.com
Technical article

Documentation from DigitalOcean explains about performing reverse DNS queries and explains what to look for.

May 2024 - DigitalOcean.com
Technical article

Documentation from RFC explains the return-path email header - use the return-path email header and then look at the DNS records of the domain.

August 2023 - RFC-Editor.org
Technical article

Documentation from Google Workspace explains how to view email headers in Gmail. You need to open the email, click the three vertical dots, and select 'Show original' to see the full headers.

March 2025 - Google