Summary
Proofpoint, a widely used email security gateway, often impacts how email authentication (SPF, DKIM, DMARC) is processed, especially for organizational Outlook domains. When emails pass through a third-party service like Proofpoint, the original authentication results can be altered or invalidated, leading to what appear as authentication failures at the receiving end, even for legitimate mail. This is a common challenge, but Microsoft 365 (formerly Office 365) is designed to handle this by using inbound connectors that trust the Proofpoint gateway, bypassing these perceived failures.
Key findings
- Authentication impact: Proofpoint's role as an email security gateway means it intercepts and processes emails before they reach the final recipient server. This can interfere with standard email authentication protocols like SPF, DKIM, and DMARC, causing them to appear broken.
- Expected behavior: For incoming emails, authentication failures due to Proofpoint are often expected. Microsoft 365's inbound connectors are designed to account for this, ensuring legitimate emails are not flagged as spam despite the authentication breakage.
- MX record bypass: Attackers may attempt to bypass third-party filtering systems like Proofpoint, delivering malicious content directly to Office 365 without passing through the intended MX record.
- Configuration sensitivity: Incorrect Proofpoint configurations or conflicts with internal email relay settings can exacerbate authentication problems, leading to deliverability issues.
Key considerations
- Inbound connector setup: Organizations using Proofpoint with Outlook domains must ensure that inbound connectors in Microsoft 365 are properly configured to trust Proofpoint's IP addresses and handle authentication failures gracefully.
- SPF record accuracy: A correctly configured SPF record is essential when using Proofpoint to prevent your domain from being blocklisted (or blacklisted) by spam filters.
- Troubleshooting: If authentication issues persist, it's crucial to examine both Proofpoint settings and Microsoft 365 configurations. Blocking domains or IPs can hinder proper diagnosis and resolution of deliverability problems.
- Internal email relay: Verify that Proofpoint settings do not inadvertently affect internal email relay within your Microsoft 365 environment, as this can create unexpected authentication failures for internal mail flow. You can learn more about how Proofpoint affects deliverability in our guide on Proofpoint and webmail deliverability.
What email marketers say
Email marketers often face complex challenges when their organizations implement email security gateways like Proofpoint, especially concerning email authentication with Outlook domains. While these systems are vital for security, they can introduce unforeseen complications that impact deliverability and the perceived authenticity of emails. Marketers frequently report issues where emails that should pass authentication checks are flagged or even rejected, necessitating a deeper understanding of how these systems interact.
Key opinions
- Authentication headaches: Many marketers find it frustrating when email authentications consistently break for their organizational Outlook domain, even when they pass perfectly fine for other recipients.
- IP discrepancies: A common observation is that authentication failures occur because the sending IP detected (e.g., 205.xx.xx.212) is not the one configured within the Proofpoint system, leading to unexpected blocks.
- Filtering challenges: Marketers frequently report the need to constantly fine-tune their safe and blocked sender lists within Proofpoint to maintain effective email filtering and ensure critical communications reach their intended recipients.
- Security vs. Deliverability: There's a constant balance between leveraging advanced email security features from Proofpoint to block threats like phishing and spoofing, and ensuring that legitimate marketing emails are not inadvertently caught or delayed.
Key considerations
- Troubleshooting process: When emails are not bouncing or going to spam but still have deliverability issues, marketers often wonder how to resolve these problems with Proofpoint.
- Internal configuration review: It's important to verify that Proofpoint settings aren't impacting internal email relay within Office 365, which can inadvertently affect authentication for internal communications.
- Compliance with new requirements: Marketers need to understand Outlook's new sender requirements to ensure their email practices align, especially when using third-party security solutions like Proofpoint.
- Threat landscape awareness: Stay vigilant against phishing campaigns where attackers impersonate cybersecurity vendors, even Proofpoint, to compromise user credentials.
Marketer view
Marketer from Email Geeks describes: We are struggling to resolve email authentications for our organizational Outlook domain, even though authentications pass for all other recipients outside our network.
Marketer view
Marketer from Email Geeks observes: Our organization uses ProofPoint, and we're seeing all email authentications break, indicating that our sending IP (e.g., 205.xx.xx.212) is not the configured sending IP within their system.
What the experts say
Experts in email deliverability and security recognize that the interaction between third-party security solutions like Proofpoint and mailbox providers, particularly Microsoft Outlook (Microsoft 365), is a common source of authentication challenges. While these issues may seem like deliverability failures, experts confirm that they are often an expected part of the mail flow when such gateways are deployed. The key lies in proper configuration and understanding how receiving servers are instructed to interpret authentication results. You can learn more about how SPF records and corporate email filters affect authentication.
Key opinions
- Gateway expectation: It is expected for authentication to appear broken when Proofpoint is positioned as an inbound email gateway for an organizational Outlook domain.
- Inbound connector role: For incoming mail to a Microsoft 365 environment, the inbound connector on 365 is designed to bypass authentication failures if they originate from a trusted Proofpoint source, preventing them from being marked as spam.
- Troubleshooting hindrance: Blocking the domain and IPs associated with Proofpoint can make it significantly harder for experts to assist in diagnosing deliverability issues.
- SPF impact: When a security gateway like Proofpoint modifies email headers or routes mail, it often impacts how original authentication results, particularly SPF, are interpreted by the receiving server.
Key considerations
- Bypassing filters: Experts warn that attackers can sometimes bypass third-party gateways like Proofpoint to deliver malicious content directly to Office 365, without the email traversing the configured MX records.
- Microsoft 365 trust: Organizations must correctly configure Microsoft 365 inbound connectors to trust the Proofpoint gateway. Failing to do so can lead to legitimate mail failing authentication checks and potentially being marked as spam.
- SPF DNS timeout: It's crucial to be aware of the hidden SPF DNS timeout that can occur with Microsoft, as it can cause authentication issues even with an otherwise correct SPF record.
- DMARC and DKIM alignment: When Proofpoint is in the mail flow, senders need to ensure their DKIM signatures remain intact and that DMARC policies properly account for the gateway's actions to prevent DKIM failures or DMARC issues.
Expert view
Expert from Email Geeks points out: If you are experiencing authentication issues with your Outlook domain, it strongly suggests that Proofpoint is deployed as an email gateway in front of your email infrastructure.
Expert view
Expert from Email Geeks explains: Such authentication failures are often expected when Proofpoint is in place, particularly for incoming emails directed to your organization's mailboxes.
What the documentation says
Official documentation from Microsoft and Proofpoint, as well as guides from email security experts, consistently emphasize the importance of proper configuration for ensuring email authentication works as intended when a security gateway is involved. They detail how services like Proofpoint fit into the mail flow and the necessary steps to prevent authentication failures from impacting legitimate email delivery, especially within a Microsoft 365 environment. This includes specific guidance on setting up connectors and managing DNS records.
Key findings
- Inbound gateway configuration: Proofpoint Protection Server is designed to function as the inbound mail gateway, processing all incoming mail for specified domains before it reaches the final destination.
- SPF authentication: Documentation confirms that the primary role of SPF is to authenticate sender identity, ensuring legitimate emails on behalf of your domain. A correctly configured SPF record is crucial to avoid blocklisting.
- Microsoft's new requirements: Microsoft has introduced new requirements and best practices to strengthen email authentication, particularly for high-volume senders, which impact how Proofpoint-protected domains interact with Outlook.
- Filtering customization: Proofpoint's email protection features include Safe Senders and Blocked Senders lists, enabling administrators to fine-tune email filtering based on their organization's needs.
Key considerations
- Integration guides: Comprehensive integration guides are available that detail how to configure Proofpoint Protection Server as the inbound mail gateway for Microsoft 365, ensuring proper mail flow and authentication handling.
- Bypass scenarios: Technical documentation often highlights scenarios where attackers can bypass third-party gateways to deliver spam or malicious content directly to Office 365, emphasizing the need for robust layered security.
- Authentication setup: Detailed instructions are provided for setting up and troubleshooting SPF, DKIM, and DMARC records, which are critical for domains using Proofpoint with Outlook.
- Spoofed email resolution: Documentation also addresses how to resolve issues where Proofpoint might identify authenticated emails as spoofed, a common challenge.
Technical article
Documentation from AutoSPF confirms: A correctly configured SPF record is pivotal for email security, specifically reducing the risk of spam filters blacklisting your domain and ensuring legitimate email delivery.
Technical article
Documentation from Microsoft TechCommunity specifies: Outlook's new requirements for high-volume senders are designed to strengthen email authentication for domains sending more than 5,000 emails daily, impacting deliverability with third-party gateways.
Related resources
10 resources
Related pages
What are the best practices for email domain authentication across corporate and marketing mail?
Why are fully authenticated emails marked as 'Unverified Sender' in Outlook/Hotmail?
Is Proofpoint commonly used for corporate email, and how does it affect webmail deliverability issues like blacklisting?
How can I resolve email deliverability issues with Proofpoint when emails are not bouncing or going to spam?
How to resolve Proofpoint identifying authenticated emails as spoofed?
How To Comply With Outlook's New Sender Requirements
A simple guide to DMARC, SPF, and DKIM
Why your emails fail at Microsoft: the hidden SPF DNS timeout
How to fix common DMARC issues in Microsoft 365 and Google Workspace
What happens when your domain is on an email blacklist?
