What is the primary purpose of the DMARC 'fo' tag?

The 'fo' tag, or failure options tag, in a DMARC record specifies which types of authentication failures should trigger the generation and sending of forensic (RUF) reports. It allows domain owners to control the granularity of the detailed failure information they receive.

What are DMARC forensic reports, and how do they differ from aggregate reports?

DMARC forensic reports (RUF reports) provide detailed, anonymized copies of individual emails that failed DMARC authentication, including headers and sometimes truncated body content. Aggregate reports (RUA reports) offer a high-level overview of DMARC compliance, showing statistics on email volume, authentication results, and policy application, without individual message details.

Is it safe to always use 'fo=1' in my DMARC record?

While 'fo=1' provides the most comprehensive failure reporting, it can lead to a very high volume of reports, which can be challenging to manage without a dedicated DMARC monitoring tool like Suped . Additionally, forensic reports can contain sensitive information, so ensure you have secure processes for handling this data.

What happens if I don't include the 'fo' tag in my DMARC record?

If the 'fo' tag is omitted from your DMARC record, its value defaults to '0'. This means you will only receive forensic failure reports if both SPF and DKIM authentication fail and are not in alignment. You would not receive reports for cases where only one of the authentication methods fails.

What DMARC 'fo' tag value requests failure reports for all failures? - DMARC - Email authentication - Knowledge base

Magnifying glass examining email failures indicated by red 'X' symbols

When setting up DMARC, one of the crucial tags you'll encounter is the fo tag, short for 'failure options.' This tag dictates what types of authentication failures should trigger the generation of forensic reports (also known as DMARC failure reports or RUF reports). Understanding its different values is essential for gaining comprehensive visibility into your email ecosystem and identifying potential threats or misconfigurations. Without proper configuration of this tag, you might miss critical information about how your domain's emails are failing authentication checks.Suped provides robust DMARC monitoring capabilities, offering AI-powered recommendations to help you interpret these reports and take corrective action, ensuring your emails reach their intended inboxes.

The choice of fo tag value directly impacts the granularity of the forensic reports you receive. While aggregate reports provide a high-level overview of DMARC compliance, forensic reports offer detailed insights into specific email failures. For many organizations, particularly those actively combating spoofing and phishing, receiving reports for all types of failures is critical to maintain a secure and reliable email sending infrastructure. The following sections will guide you through the specifics of the fo tag and how to use it effectively.

Understanding the DMARC 'fo' tag

The fo tag is an optional component within your DMARC record that determines when forensic failure reports should be generated and sent. These reports contain anonymized copies of messages that failed DMARC authentication, offering valuable diagnostic information. By default, if the fo tag is omitted, its value defaults to 0, meaning forensic reports are only sent if both SPF and DKIM authentication fail and are not in alignment.

To effectively use DMARC, it is crucial to understand the implications of each fo value. Forensic reports, while detailed, can sometimes contain sensitive information. This is why many organizations prefer to start with the default fo=0 and only escalate to more comprehensive reporting once they have a clear understanding of their email flows and have established secure channels for handling such data. Remember, DMARC reports are key to achieving email security goals.

The fo tag's specification is outlined in the DMARC RFC, providing clear guidelines for its use. A comprehensive understanding of DMARC tags ensures that you can craft a policy that perfectly matches your organizational needs and security posture. You can find more details on these options and their meanings on the DMARC 'fo' tag options and meanings page from DuoCircle.

The 'fo' tag values

The fo tag can take on four possible values, each specifying a different condition for generating forensic reports:

Value	Description	Condition for Forensic Report Generation
0	SPF and DKIM all fail	Reports sent only if both SPF and DKIM authentication fail AND neither are aligned.
1	Any failure	Reports sent if any authentication mechanism (SPF or DKIM) fails to produce a DMARC pass.
D	DKIM failure	Reports sent if the DKIM authentication mechanism fails for any reason.
S	SPF failure	Reports sent if the SPF authentication mechanism fails for any reason.

From the table above, it's clear that the fo tag value that requests failure reports for all failures is 1. This setting ensures that you receive a forensic report whenever an email purporting to be from your domain fails either SPF or DKIM alignment, even if the other mechanism passes. This provides the most comprehensive view of authentication failures, allowing for a deeper investigation into potential issues like spoofing attempts or legitimate misconfigurations.

Spotlight on emails showing various authentication results

Requesting all failure reports with 'fo=1'

Setting fo=1 is a powerful configuration for your DMARC record. It means that if an email fails SPF authentication or DKIM authentication and its alignment requirements are not met, you will receive a forensic report. This level of detail is invaluable for diagnosing issues that might otherwise go unnoticed, such as a third-party sender failing only one authentication method or a legitimate sending source that needs configuration adjustments.

While fo=1 offers maximum visibility, it can also lead to a higher volume of reports. For organizations with many sending sources, managing these detailed reports can become overwhelming without the right tools. Platforms like Suped are designed to parse and present DMARC reports, including forensic ones, in an easily digestible format, providing actionable recommendations to address any identified issues. You can learn more about how Microsoft handles DMARC reports on their dedicated page.

Best practices for 'fo=1'

Start small: Begin with a p=none policy to monitor impacts without affecting delivery.
Dedicated email address: Use a specific email address for RUF reports to manage volume.
Use a DMARC platform: A tool like Suped is invaluable for processing, storing, and visualizing RUF and RUA reports.

Implementing 'fo' in your DMARC record

To implement fo=1, you need to add or modify the fo tag within your DMARC DNS record. It typically appears alongside other DMARC tags like v, p, rua, and ruf. The ruf tag specifies the email address where these detailed failure reports should be sent.

Example DMARC record with fo=1DNS

v=DMARC1; p=none; fo=1; rua=mailto:dmarc_aggregate@yourdomain.com; ruf=mailto:dmarc_forensic@yourdomain.com

In this example, fo=1 ensures that a forensic report is generated for any DMARC authentication failure, whether it's an SPF or a DKIM issue. The reports are then sent to dmarc_forensic@yourdomain.com. It's important to remember that for forensic reports to be delivered to an external domain, you typically need to configure a specific DNS record to authorize the receiving server. You can generate your DMARC record with our free DMARC record generator.

Using fo=0 (Default)

Report trigger: Only when both SPF and DKIM fail DMARC alignment.
Report volume: Lower, focuses on severe failures.
Use case: Initial stages of DMARC deployment, or when forensic reports are handled manually.

Using fo=1 (All Failures)

Report trigger: When either SPF or DKIM fails DMARC alignment.
Report volume: Higher, provides comprehensive insight into all failures.
Use case: Advanced DMARC policies, active threat detection, and detailed troubleshooting.

For Managed Service Providers and businesses managing multiple domains, choosing the right fo value and having a robust DMARC monitoring platform is paramount. Suped offers a unified platform that integrates DMARC, SPF, and DKIM monitoring, alongside blocklist and deliverability insights, making it an ideal solution for comprehensive email security and management.

Maximizing DMARC insights

The DMARC 'fo' tag is a critical component for gaining detailed insights into your email authentication failures. While its default setting ('fo=0') provides reports only for complete failures, setting 'fo=1' ensures you receive forensic reports for all types of authentication failures, whether SPF, DKIM, or both. This granular reporting is invaluable for identifying subtle misconfigurations, detecting sophisticated spoofing attempts, and ultimately strengthening your email security posture.

Choosing to deploy fo=1 demonstrates a commitment to thorough email security. However, it requires a robust system for managing and interpreting the increased volume of reports. This is where DMARC platforms like Suped excel. Suped offers real-time alerts and AI-powered recommendations, transforming raw DMARC data into actionable insights that help you quickly address issues and move your DMARC policy towards enforcement (quarantine or reject).

By actively monitoring your DMARC reports with Suped, you can maintain high email deliverability, protect your brand from spoofing and phishing, and ensure your legitimate emails reach the inbox as intended. Our platform simplifies DMARC management for everyone, from small businesses to large enterprises and MSPs, making email security accessible and effective.