Summary
The X-Originating-IP email header, which indicates the IP address from which an email message originated, generally has a minimal direct impact on modern email deliverability. While it can offer clues for abuse detection and historical tracing, contemporary spam filters primarily rely on other, more reliable indicators such as the sending IP address, domain reputation, and authentication protocols (SPF, DKIM, DMARC). Filters are sophisticated enough to parse the Received headers which explicitly state the connecting IP, diminishing the importance of less trustworthy X-headers. However, it's worth noting that this header is still commonly included by many mail providers, including Microsoft 365, serving a role in their internal logging and anti-abuse efforts.
Key findings
- Limited direct impact: While historically used for blocking, the X-Originating-IP header plays a minimal role in modern deliverability decisions by ISPs and email service providers (ESPs). Modern filters focus on the actual sending IP and domain reputation.
- Focus on main IP: Email deliverability primarily hinges on the reputation of the IP address from which the mail transfer agent (MTA) sends the email, often referred to as the sending IP. This is the IP that connects directly to the receiving mail server.
- Spoofing risks: The X-Originating-IP header can be easily spoofed, making it an unreliable indicator for critical filtering decisions. Spammers sometimes attempt to manipulate it for misdirection.
- Anti-abuse and logging: This header is primarily used for anti-abuse purposes and internal logging by mail providers, helping them trace the origin of suspicious messages for forensic analysis rather than real-time filtering.
- Common inclusion: Many free email providers and services like Microsoft 365 include the X-Originating-IP header by default, though it can often be disabled with specific configurations.
Key considerations
- Prioritize core authentication: Ensure your domain has robust SPF, DKIM, and DMARC records properly configured. These are far more influential in determining email deliverability than X-Originating-IP.
- Maintain strong IP reputation: Focus your efforts on maintaining a positive reputation for your primary sending IP addresses. This includes consistent sending volume, low complaint rates, and avoiding getting blocklisted.
- Understand its purpose: While not directly impacting deliverability, understanding that X-Originating-IP is used for internal abuse detection can still be useful for troubleshooting if a specific IP is flagged for suspicious activity. More information can be found on Mutant Mail's blog.
What email marketers say
Email marketers often focus on the more direct and tangible aspects of deliverability, such as list hygiene, engagement, and sender reputation. While they may encounter X-Originating-IP in headers, their primary concern revolves around the reputation of their actual sending IP and domain, as these are the factors that most directly influence inbox placement. Some marketers might have historical experience with this header impacting deliverability, especially when dealing with older filtering systems or specific ISP quirks, but modern strategies tend to look past it.
Key opinions
- Primary focus on sending IP: Marketers largely agree that the reputation of the IP address actually sending the email is paramount. This IP dictates how various internet service providers (ISPs) treat an email, influencing whether it reaches the inbox or is filtered to spam. This is also covered in our article on IP address location and deliverability.
- Domain reputation is crucial: Alongside IP reputation, domain reputation is a critical factor influencing overall sender reputation and, consequently, email deliverability rates. Both combine to form a holistic view for receiving servers.
- Dedicated IP control: Some marketers prefer dedicated IPs to have full control over their deliverability, as actions of other senders on shared IPs can negatively impact their reputation.
- Impact of invalid emails: Sending to invalid or non-existent email addresses is consistently cited as a practice that significantly harms deliverability, irrespective of header details.
- M365 default: The X-Originating-IP header is often included by default with services like Microsoft 365, though it can often be removed via outbound filters.
Key considerations
- Monitor IP and domain reputation: Regularly check your IP and domain reputation using tools like Google Postmaster Tools. A low reputation is a primary reason for emails being filtered to spam.
- Maintain list health: Prioritize maintaining a clean and engaged email list to avoid issues like spam traps and high bounce rates, which are key determinants of deliverability.
- Implement authentication: Ensure proper SPF, DKIM, and DMARC authentication are in place. These technical configurations are fundamental to proving your legitimacy as a sender.
- Evaluate header impact: While X-Originating-IP is less critical, understanding all email headers can provide valuable clues when investigating deliverability issues. More information on email headers is available.
Marketer view
An email marketer from Email Geeks notes that the X-Originating-IP header is often included by default, particularly with services like Microsoft 365. However, they indicate that this header can typically be removed or managed by implementing an outbound filter, offering senders more control over the information revealed about the email's true origin.
Marketer view
A marketer from Nonprofit Hub highlights that reaching out to contacts from different IP addresses might negatively affect a sender's reputation, directly impacting an organization's overall standing. This suggests that consistency in sending infrastructure, rather than specific headers, is key to maintaining good deliverability. The focus should be on the sending IPs and their consistent good behavior.
What the experts say
Experts in email deliverability and anti-abuse generally agree that while the X-Originating-IP header has historical significance for abuse detection, its direct impact on deliverability has waned. Modern filtering systems are much more sophisticated, relying on the actual IP from which the email connected to the receiving server (as recorded in the Received header), along with robust authentication mechanisms and sender reputation metrics. They note that the X-Originating-IP is prone to spoofing, making it less reliable for real-time blocking decisions.
Key opinions
- Historical abuse tool: Experts confirm that X-Originating-IP was primarily used for blocking spam originating from ISPs (Internet Service Providers) in earlier days, especially when content filtering was less advanced.
- Less relevant for modern filtering: Today, receiving mail servers can walk headers to find the connecting IP, rendering the X-Originating-IP less essential for filtering based on origin.
- Trustworthiness issues: The header's value cannot always be trusted, as spammers frequently attempt to fake it for misdirection or due to a lack of understanding of email header mechanisms. This is why real IP alignment is important.
- ISP vs. ESP perspective: While ISPs might have historically used such headers for internal logging of the injecting IP, ESPs (Email Service Providers) typically focus on the standard Received headers.
- Anti-abuse efforts: The header's current utility is more aligned with anti-abuse measures, helping providers track sources of illicit mail, rather than determining general deliverability for legitimate senders.
Key considerations
- Understand header roles: Distinguish between headers critical for deliverability (like Received and authentication headers) and those primarily for diagnostic or anti-abuse purposes, such as X-Originating-IP. Our utility of X-Originating-IP article provides deeper insights.
- Focus on reputable sending infrastructure: Ensure your email sending infrastructure (whether your own servers or an ESP) adheres to best practices, including proper IP reputation management and avoidance of blocklists (or blacklists).
- Prioritize authentication: Invest in robust authentication (SPF, DKIM, DMARC) as these provide cryptographically verifiable proof of sender legitimacy, far outweighing the importance of less secure X-headers. Mailchimp's resources on IP reputation offer valuable context.
Expert view
An expert from Email Geeks suggests that the X-Originating-IP header might be used in some contexts for 2nd-received-line filtering. However, they also question the wisdom of including it in outbound mail unless the sender implicitly wants filtering based on it, suggesting it's not a standard or advisable practice for deliverability.
Expert view
An expert from Email Geeks explains that mail servers don't necessarily need the X-Originating-IP value to perform 2nd-received-line filtering; they can simply traverse other headers. They also highlight a significant issue with the header's trustworthiness, noting instances where spammers attempt to fake it, either for misdirection or due to their own lack of understanding of email headers.
What the documentation says
Official documentation and technical guides primarily describe X-Originating-IP as an optional, non-standard email header. Its main documented purpose is to assist in identifying the IP address of the originating client or relay, particularly in scenarios involving webmail interfaces or internal network setups. While it can be useful for diagnostics and abuse investigation, documentation emphasizes its limitations, such as potential spoofing and privacy concerns, which reduce its reliability as a primary signal for deliverability decisions by receiving mail servers.
Key findings
- Diagnostic aid: Documentation suggests that the X-Originating-IP header is useful for pinpointing the source of a message for investigative purposes, particularly in identifying spam or phishing campaigns.
- Flaws and limitations: Despite its utility, this header is acknowledged to have flaws, including susceptibility to spoofing and raising privacy concerns, which limits its effectiveness as a definitive indicator for filtering.
- Clues for investigation: The header can provide valuable clues when examining suspicious messages, offering insights into the sender's origin that might not be immediately apparent from standard headers.
- Tracing fraudulent senders: It assists in tracing emails back to their source IP addresses, a process that helps to identify and track fraudulent senders involved in scams, spam, and phishing attacks.
Key considerations
- Rely on standard headers: For critical deliverability, trust the Received headers which are mandated by RFCs and accurately log the path of an email, including the IP that directly connected to the server. Our blog on RFC 5322 provides more context.
- Understand its secondary role: While X-Originating-IP offers forensic value, it should not be the primary focus for senders aiming to improve inbox placement. Focus instead on email authentication and sender reputation. More details on unmasking this header can be found in technical discussions.
- Implement DMARC for robust policy: For true protection against spoofing and to control what happens to unauthenticated mail, implement a strong DMARC policy (p=quarantine or p=reject). This leverages the reliable SPF and DKIM authentication results.
Technical article
Documentation from Mutant Mail states that while the X-Originating-IP header can help in identifying message sources, it is not without flaws. These include the risks of spoofing and legitimate privacy concerns, which can complicate its use as a reliable indicator for filtering.
Technical article
Documentation from Proton explains that X-headers, such as the X-Originating-IP field, reveal the sender's IP address. This information can serve as a useful clue when investigating potentially suspicious messages, aiding in the detection of malicious activity.
Related resources
13 resources
Related pages
What is the utility of X-Originating IP in email headers?
Should my origination IP and outbound IP be the same when sending email?
What happens when your ip gets blocklisted?
A simple guide to DMARC, SPF, and DKIM
Why Your Emails Are Going to Spam in 2024 and How to Fix It
Does a new dedicated IP for transactional emails fix existing deliverability problems?
Does IP address location affect email deliverability?
What RFC 5322 Says vs. What Actually Works
How email blacklists actually work: a simple guide
How do email sending practices impact domain reputation and deliverability?
