Email remains one of the primary channels for business communication; however, it is also one of the most common vectors for cyber threats such as phishing, spoofing and business Email compromise. With Microsoft Office 365 becoming more prevalent in organizational use, ensuring that your organization’s Email ecosystem is secure is no longer optional — it is crucial to maintain trust with stakeholders and protect the operational integrity of your business.
This is where domain-based Message Authentication, Reporting and Conformance (dmarc) comes into play. In this guide to DMARC for Office 365, we will provide you practical insight on how to monitor and analyze Email authentication, so you can better protect your organization from threats based on Email.
What is DMARC, and why is it important for Office 365 users?
DMARC is an Email authentication protocol designed by domain owners to protect their domains from unauthorized use, commonly known as Email spoofing. DMARC builds upon two existing protocols, the Send Policy Framework (SPF) and Domain Keys Identified Mail (DKIM), to validate incoming Email messages. When correctly implemented, DMARC helps prevent attackers from sending emails that appear to have been sent by a trusted domain.
For Office 365 users, the importance cannot be overstated. With more businesses moving to cloud services, attackers are targeting Office 365 domains at an alarming rate. A well-implemented DMARC policy does not just help protect your brand’s reputation, but also reduces the chances of your communications being marked as spam or rejected by receiver servers.
Setting Up DMARC in Office 365: A Step-by-Step Overview
Implementing DMARC in an Office 365 setting is somewhat more involved than in other settings. First, you will have to set up SPF and DKIM for all your domains. SPF tells what mail servers are allowed to send mail on your company’s behalf. The DKIM identifies the sender via a digital signature, allowing them to check if it was sent from your domain.
Once SPF and DKIM are configured, you can create a DMARC policy in the DNS for your domain. Your DMARC policy informs the mail server handling your email as to what action they should take when sending email that has failed the authentication test. DMARC policy options include “none” (only monitoring), “quarantine” (redirecting unverified emails to the spam folder) and “reject” (blocking verified emails)
This guide to DMARC for Office 365 emphasizes the importance of starting with a ‘none’ policy, which allows you to collect data without impacting mail delivery. Over time, as you analyze reports and address authentication issues, you can move toward stricter enforcement for optimal protection.
Monitoring DMARC: Understanding Aggregate and Forensic Reports
One of the most important parts of implementing DMARC is to continually monitor it. DMARC will send out two different report types, an aggregate report (RUA) and a forensic report (RUF). The RUA will show an overview of all emails sent using your domain. It will also list whether each message was authenticated successfully or if it wasn’t. If a message wasn’t authenticated successfully, the reason(s) why won’t be provided by the RUA. However, the RUF provides additional information about specific messages that didn’t pass a DMARC check.
Office 365 does not have native DMARC reporting capabilities; however, you are able to include the address of a non-Office 365 account when you set up your DMARC DNS records so that you can receive the reports. In many cases, companies utilize third party DMARC analysis tools to analyze and graphically display the XML based reports. This helps convert “raw” data into “actionable” intelligence.
Any good resource outlining how to implement DMARC for Office 365 should highlight the importance of these reports. You can find potential unauthorized usage of your domain, identify misconfigured settings, track your progress with tightening your DMARC policy, etc., through regular review of your aggregated data.
Analyzing Authentication Failures: Common Causes and Solutions
Ultimately, you’ll experience failed authentications while you are evaluating your DMARC implementation. Consequently, it’s imperative to understand the most common causes of failed authentications and how to address those issues. Most commonly occur due to:
Mistakes in setting up SPF (Sender Policy Framework), and/or DKIM (DomainKeys Identified Mail): Check that all email service providers that you want to authorize to send emails using your domain name are included within your SPF record; and verify that you include DKIM signatures for each of your sending domains.
Forwarded messages: A forwarded message can fail DMARC because a forwarding server may either remove or modify the original authentication data.
Third-party senders: Any marketing platform, CRM software application, etc. which sends emails on your behalf will need to be properly registered into your SPF/DKIM records.
You should develop a methodical procedure to track down failure events through analysis of the DMARC reports to identify where the failure was created, whether the failure event was valid or not, and then perform any required changes to your records. Using the described feedback loop methodically will be a key component of any “Guide to DMARC for Office 365,” and will assist in protecting against potential phishing/spamming attempts and improve overall delivery.
Leveraging Third-Party Tools for DMARC Management
A number of third-party platforms can assist in processing, visualizing and notifying of DMARC reporting data; this makes it simpler for security teams to detect trends or react quickly when an incident occurs.
In addition to visualization dashboards which indicate authentication success/failure rates and flag potential anomalies, many also provide recommendations for remediation. Additionally, some of these third party vendors have integrated their functionality into SIEM (Security Information & Event Management) products so that administrators can monitor all aspects of their security from one single interface.
When implementing a comprehensive guide to using DMARC with Office 365, organizations may want to evaluate use of one of these third-party platforms as they will simplify the overall administrative process and increase the effectiveness of your organization’s DMARC policy.
Evolving Your DMARC Policy: From Monitoring to Enforcement
A successful DMARC deployment is not a single event but rather a continuous process. The first step in deploying DMARC will be to deploy the ‘None’ Policy to allow you to gather baseline information. Next, as you become confident that your authentication has been properly set up, you can start moving towards more restrictive Policies (Quarantine) before finally implementing the most restrictive policy available (Reject).
A gradual rollout of more restrictive Policies will limit the amount of disruption to your end-users while at the same time protecting your Domain from Spoofing and Phishing. In addition to regularly reviewing your DMARC Reports, and making updates to your TXT Records when necessary due to new Email Services being deployed, it would also be advisable to educate your End-Users on Authentication Best Practices. This is what we mean by a Mature DMARC Strategy in an Office 365 Environment.
Real-World Impact: Case Examples and Lessons Learned
A medium-sized business shifted from its own on-premises Microsoft Exchange server to Office 365 and almost immediately realized that there was an increase in phishing emails which were spoofed using its domain name. The business followed a step-by-step procedure to set up DMARC for Office 365. In order to establish this process the business first needed to implement SPF, DKIM, and DMARC. They started by establishing a “monitor” DMARC policy. After the business had successfully established SPF and DKIM policies to authenticate all of the company’s legitimate senders, it then switched to a “quarantine” DMARC policy and eventually to a “reject” DMARC policy.
The success of implementing these steps resulted in a dramatic decrease in phishing attempts and in turn, a decrease in the number of suspicious emails that employees received. It is also important to note that after setting up these policies the business could continue to monitor potential issues as they arose. Therefore, the business remained vigilant regarding future potential issues while continuing to provide uninterrupted email services.
Best Practices for Ongoing DMARC Success in Office 365
To effectively establish and maintain an effective DMARC policy within Office 365; you need to be very proactive with all aspects and details. The following is a list of some of the best practices for establishing an effective DMARC policy:
- Update SPF, DKIM, and DMARC records regularly: As your email infrastructure evolves, make sure that you check on and update your DNS records regularly.
- Review reports continuously: Continuously schedule your DMARC reports for review so that you can identify problems sooner rather than later.
- Educate your stakeholders: Make certain that both IT personnel and Business users have an understanding of why email authentication is important.
- Test your new configurations prior to enforcing them: Test your new configurations (DMARC) using staging environments or phasing deployments to ensure that you don’t disrupt the flow of legitimate email messages into your environment.
Use automation whenever possible: Use third party tools to minimize manual effort and maximize response time.
If you follow these best practices continually, they will enable you to get the maximum benefit from your DMARC investment and protect your organizations’ reputation.
Conclusion: Building a Secure Email Ecosystem with DMARC
As new threats emerge and evolve daily, an active and well-informed stance toward email security will be necessary. DMARC is a highly effective way to prevent spam attacks by blocking email spoofing, reducing your company’s exposure to phishing emails and increasing trust in the authenticity of all email communications sent digitally. This guide to DMARC for Office 365 makes it clear that the best practice for successful implementation of DMARC in Office 365 is monitoring and evaluation of performance after initial setup. Your organization should monitor the status of its email communications channel at all times to remain secure and protected from emerging threats.
DMARC has been implemented in your Office 365 environment. Remember — Security is an Ongoing Process. Utilize this Guide to DMARC for Office 365 as a Roadmap for Continuous Improvement Protecting Not Only Your Company But Also Your Customers/Partners/Stakeholders From Spam Threats. See more