How can I check if an email is sent from a dedicated or shared IP without contacting the ESP?
Summary
What email marketers say11Marketer opinions
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.
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.
Email marketer from MailchimpCommunity.com shares to use inbox placement tests. Review report to see all the IPs that the messages came from.
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.
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.
Email marketer from Neil Patel explains that you can check the email headers to find the IP address the email was sent from.
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.
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.
Email marketer from stackoverflow.com shares to check SPF and DKIM records to see how many domains are sending email from the IP
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.
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.
What the experts say5Expert opinions
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.
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.
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.
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.
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.
What the documentation says5Technical articles
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.
Documentation from Microsoft shares to look for the 'Received' header which will reveal the IP that the email was sent from.
Documentation from DigitalOcean explains about performing reverse DNS queries and explains what to look for.
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.
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.