Why am I seeing DMARC errors when sending to Gmail from MXroute?
Matthew Whittaker
Co-founder & CTO, Suped
Published 27 Jun 2025
Updated 18 Aug 2025
6 min read
It can be confusing and frustrating to receive DMARC errors when sending emails from your domain hosted on MXroute, especially when these bounces contain a 550-5.7.26 Google DMARC error. The situation becomes even more puzzling when the X-Failed-Recipients header points to a Gmail address you never directly sent to.
This usually indicates that the email from your domain, hosted on MXroute, is being forwarded to a Gmail account. While your domain's email authentication, including SPF, DKIM, and DMARC, might be perfectly configured for direct sending, forwarding introduces complexities that can disrupt this authentication chain.
When an email is forwarded, it passes through an intermediary server. This server, even if it's legitimate, becomes the 'new' sending server from the perspective of the final recipient's mail server. This change in the sending path is where DMARC (Domain-based Message Authentication, Reporting, and Conformance) issues often arise, leading to rejection by providers like Gmail due to unauthenticated mail.
DMARC is a critical email authentication protocol that builds upon SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to verify the legitimacy of an email sender. For an email to pass DMARC, it must pass either SPF or DKIM, and critically, the domain in the From header (the visible sender) must align with the domain that passed SPF or DKIM. This alignment is where email forwarding often causes problems.
When an email is forwarded through a service like MXroute, the IP address sending the email to Gmail is MXroute's, not your original sending server's. For SPF to pass, MXroute's IP address would need to be included in your domain's SPF record. However, forwarding typically doesn't entail adding the forwarding server to your SPF record. Consequently, the SPF check against your Return-Path (or MailFrom) domain usually fails, leading to an SPF alignment failure for DMARC.
While some forwarding services implement ARC (Authenticated Received Chain) to preserve authentication results across hops, MXroute has stated that they do not use ARC. They do attempt to rewrite the return path using SRS (Sender Rewriting Scheme), which helps with bounce handling, but SRS doesn't resolve the DMARC SPF alignment issue for the From header. This fundamental mismatch is the primary reason for DMARC failures when forwarding emails.
Why Gmail is rejecting these forwarded emails
Gmail has progressively implemented stricter email authentication requirements to combat spam and phishing. When an email arrives at a Google mailbox (including Gmail and Google Workspace accounts), it performs a series of checks, including SPF, DKIM, and DMARC. If an email fails DMARC, Gmail will strictly adhere to the domain's DMARC policy (the p= tag in your DMARC record).
For many domains, the DMARC policy is set to p=quarantine (send to spam) or p=reject (block completely). The 550-5.7.26 error message clearly indicates that Gmail has rejected the email due to a DMARC authentication failure. This is not necessarily an issue with your initial email configuration, but rather how the email is handled during the forwarding process.
If your domain has a DMARC policy of p=reject, any email failing DMARC, including those forwarded in a way that breaks alignment, will be rejected outright. This is a common reason why you might see such errors for emails ultimately destined for Gmail addresses. Understanding how DMARC impacts Gmail deliverability is key.
Steps to troubleshoot and prevent DMARC failures with forwarding
The simplest solution to avoid DMARC failures due to forwarding is to not forward emails from a DMARC-enforced domain to Gmail. If you must receive emails in Gmail that are sent to your MXroute-hosted domain, consider configuring Gmail to fetch emails via POP3 or IMAP directly from MXroute. This bypasses server-side forwarding and preserves the original email authentication.
Regardless of forwarding, ensure your domain's core email authentication is robust. This includes correctly configured SPF, DKIM, and DMARC records. Regularly check your DNS settings to ensure there are no errors or outdated entries. A well-configured DMARC record could look like this:
Monitoring your DMARC reports is crucial for identifying authentication issues. These XML reports provide insights into how receiving mail servers, including Google (logo: google.com), are evaluating your emails. By analyzing these reports, you can pinpoint specific failures, whether related to forwarding or other configuration issues, and take corrective action. This helps in understanding why you receive DMARC failure reports.
The information in DMARC reports (RUA for aggregate reports and RUF for forensic reports) is invaluable. Aggregate reports summarize authentication results, while forensic reports provide more detailed insights into individual failures, helping you understand DMARC reports from Google and Yahoo. Consistent monitoring can help you detect unexpected issues, such as email forwarding causing DMARC failures, and manage your domain's overall sender reputation to avoid being placed on a blocklist or blacklist.
Views from the trenches
Best practices
Configure SPF, DKIM, and DMARC records correctly on your domain’s DNS to establish a strong sending identity.
Avoid direct server-side email forwarding to Gmail from domains with a DMARC policy of p=reject or p=quarantine.
Utilize DMARC reporting to gain visibility into email authentication results and identify sources of failures.
Common pitfalls
Assuming DMARC failures are always due to misconfiguration of your primary sending service rather than forwarding.
Ignoring DMARC reports, which contain critical information about authentication issues and potential abuse.
Not understanding that SRS (Sender Rewriting Scheme) does not address SPF alignment for DMARC on the 'From' header.
Expert tips
For critical email flows, explore alternatives to forwarding, such as setting up a mailbox in Gmail to pull messages via POP3 or IMAP.
Implement a gradual DMARC rollout, starting with p=none to monitor results before moving to stricter policies like p=quarantine or p=reject.
Continuously review your email logs and bounce messages for specific error codes like 550-5.7.26 to quickly diagnose issues.
Expert view
Expert from Email Geeks says that MXroute does not use ARC (Authenticated Received Chain) but implements SRS (Sender Rewriting Scheme) to try and maintain return-path integrity. This can lead to DMARC failures when forwarding to mailboxes like Gmail that strictly enforce DMARC and require proper authentication alignment.
2024-04-16 - Email Geeks
Marketer view
Marketer from Email Geeks says that auto-forwarding emails to Gmail often triggers DMARC failures, which is a common issue email senders encounter.
2024-04-16 - Email Geeks
Maintaining deliverability with DMARC and forwarding
Encountering DMARC errors from Gmail when sending via MXroute often points to an underlying email forwarding scenario. While your domain’s direct email authentication setup might be correct, the act of forwarding can break SPF alignment, leading to DMARC failures because the forwarding server's IP isn't authorized in your domain's SPF record. Gmail's strict adherence to DMARC policies then results in the rejection of these unauthenticated messages.
To prevent these issues, the most effective approach is to avoid server-side forwarding from DMARC-enforced domains to Gmail. Instead, consider fetching emails directly into your Gmail account via POP3 or IMAP. Continuous monitoring of DMARC reports remains essential to identify and troubleshoot any authentication discrepancies.
By understanding the nuances of how DMARC interacts with email forwarding, you can maintain strong email deliverability, ensure your messages reach their intended recipients, and avoid being listed on a blocklist or blacklist. Properly managing your email flow, especially when involving third-party services like MXroute and stringent receivers like Gmail, is key to a healthy sending reputation.
Gmail address you never directly sent to.
Google mailbox (including Gmail and Google Workspace accounts), it performs a series of checks, including SPF, DKIM, and DMARC. If an email fails DMARC, Gmail will strictly adhere to the domain's DMARC policy (the p= tag in your DMARC record).
