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Authenticate Emails with DMARC for Better Deliverability

Authenticate Emails with DMARC for Better Deliverability

Email is a wonderful opportunity for businesses to promote their brand and get clients. From the other hand, email facilitates the spreading of spam, phishing, malware, viruses and other fraud simply because it is difficult to tell if the sender is really the one it pretends to be.

Legitimate senders have to wade through complicated anti-spam filters just to get their emails delivered to the destination user.

To help email senders deliver legitimate emails to the recipients and block phishing and fraud messages, a new email authentication standard was adopted by email senders and receivers.

1. DMARC Overview

DMARC – Domain-based Message Authentication, Reporting & Conformance – is a mechanism to determine whether an email message is coming from the particular sender or not. It is designed to protect the company’s email domain from being used for email spoofing, sending phishing scams and other malware.

DMARC is built on the widely deployed SPF and DKIM protocols and adds domain alignment checking and reporting capabilities. DMARC reports are generated by the organizations that process incoming emails and give domain owners visibility on how their domains are used on the Internet.

Senders and organizations use DMARC to check that their sending domains are not abused and that they don’t send any fraud emails.

By implementing the DMARC authentication, email senders can make sure that they did everything they could to prevent the abuse of their domains, stop spoofed messages and protect their brand.

2. Why DMARC is Important

To tie all of the above, DMARC provides the following benefits to domain owners:

1. Prevention of fraud emails.

If you implement DMARC and make all of your legitimate email sources DMARC aligned, you can tell the email receivers to reject any email that claims to come from your domain but fails the DMARC check. DMARC gives you a powerful anti-phishing control and has been used to block huge amounts of email fraud.

2. Simplified delivery to the recipient’s Inbox.

DMARC makes it easy for email receivers to identify the message. To stop spam, email receivers invest a lot of time, money, and resources in developing technology that filters out unwanted emails. The DMARC adoption allows email receivers to simplify their filtering rules, quickly identify the email and deliver it. If an email passes DMARC authentication, it means it truly comes from the domain displayed in the From address.

3. Protection of the domain and brand reputation.

By analyzing DMARC reports, you can identify illegal senders using your domain and tell the receivers to reject an email sent from your domain if it doesn’t pass the DMARC check. This way you can reduce the number of unsolicited emails coming from your domain that can hurt your sender reputation, brand, and ROI.

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4. Email traffic control.

The deployment of DMARC allows you to have full control over your email sources and make sure that they send only legitimate messages that your subscribers want. You can see whether or not your legitimate sending sources pass the SPF and DKIM check and you can fix the authentication issues when they occur. Organizations can use DMARC to monitor how their partners send emails on their behalf and if everything is sent correctly. This allows you to reduce the risk of having your sending IP/domain blacklisted for sending spam emails.

Authenticate Emails with DMARC

DMARC becomes a “must-have” for anyone who cares about email deliverability. If your emails are not DMARC compliant, they are competing with spam and fraud emails for a place in the user’s Inbox.

3. How DMARC Works

DMARC is built on the base of the two other authentication methods SPF and DKIM.

SPF and DKIM authenticate various aspects of an email message: SPF authenticates the domain that appears in the “Envelope From” address, and DKIM authenticates the domain found in the d= tag inside a DKIM-signature in the email header.

These domains are typically not visible to the recipient which makes it possible to spoof the email “From” address.

The results of SPF and DKIM checks create the Authenticated Identifiers.

In the case of SPF, identifier alignment means that the domain of the “Envelope From” address has to align with the domain in the header “From” address. When the “Envelope From” address is empty, alignment is checked against the EHLO domain.

In the case of DKIM, identifier alignment means that the domain found in the d= field of a DKIM-signature in the email header has to align with the domain found in the header “From” address.

There are two modes in identifier alignment: strict and relaxed.

The strict mode requires the two domains to be identical in order for them to be in alignment. For example, domain.com aligns with domain.com in strict mode, but it doesn’t align with mail.domain.com.

The relaxed mode doesn’t require the two domains to match exactly. As long as the organizational domains match, they align with each other. For example, domain.com aligns with domain.com and also aligns with mail.domain.com.

Because anyone can register a domain and set up SPF and DKIM, DMARC hardens the authentication process by connecting the results of processing SPF and DKIM — the Authenticated Identifiers — with the header “From” field. The Authenticated Identifiers have to be related to the domain found in the “From” header field. This concept is referred to as “Identifier Alignment”.

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When the following conditions are true for an email message, the email is DMARC aligned:

– SPF authentication passes and has identifier alignment; and/or

– DKIM authentication passes and has identifier alignment.

Authenticate Emails with DMARC

When an email is DMARC aligned, it passes DMARC authentication. It means that the email is truly sent from the email address displayed to end users.

There are two aspects about DMARC:

1. DMARC policy.

DMARC allows you to tell the email receiver how to handle an email if it fails the DMARC authentication.

There are 3 policies:

– none, also called the monitoring mode, (no action is taken, recommended to collect DMARC reports);

– quarantine (the email is moved to the spam folder);

– reject (the email is rejected outright and is never delivered).

You specify the DMARC policy in a DMARC record, where the policy appears in the p tag, like p=none.

2. DMARC reports.

DMARC provides reporting capabilities to allow email domain owners to gain visibility into how their email domain is used across the Internet and which email sources are sending from it.

The feedback comes in a form of a report which is sent by the incoming email processor to the email address specified in the DMARC record, for example, rua=mailto:support@domain.com.

You can receive 2 types of reports: aggregate reports (stand for the rua= tag in the DMARC record) and forensic reports (stand for the ruf= tag in the DMARC record).

DMARC aggregate reports provide a comprehensive view of all of a domain’s traffic: sending sources, percentages of emails passing/failing SPF and DKIM, percentages of emails DMARC compliant and non-compliant.

Aggregate reports provide valuable feedback about the health of your email domain, help you determine authentication issues, identify illegal sending sources and stop malicious activity.

Authenticate Emails with DMARC

Forensic reports show individual emails that are not compliant with DMARC.

Authenticate Emails with DMARC

4. How to Deploy DMARC

The process of deploying DMARC for your outgoing emails is simple:

1. Create a DMARC record.

2. Publish the DMARC record to the DNS of your domain.

3. Analyze the data and modify your sending sources as appropriate.

A DMARC record consists of DMARC tags. The below list shows what each tag possibly found in a DMARC record means:

v: DMARC protocol version. The default is “DMARC1”.

p: policy applied to an email sent from the domain that fails the DMARC check. Example: p=quarantine.

sp: policy applied to an email sent from the subdomain that fails the DMARC check. Example: sp=reject.

pct: percentage of messages subjected to filtering. Example: pct=20 tells email receivers to only apply the ‘p=’ policy 20% of the time against emails that fail the DMARC check. This only works for the “quarantine” and “reject” policies.

rua: reporting URI of aggregate reports. Example: rua=mailto:agg_reporting@domain.com.

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ruf: reporting URI of forensic reports. Example: rua=mailto:for_reporting@domain.com.

fo: forensic options. Allowed values: ‘0’ to send reports if both DKIM and SPF fail, ‘1’ to send reports if either DKIM or SPF fails, ‘d’ to send a report if DKIM failed and ‘s’ if SPF failed.

rf: reporting format for forensic reports.

adkim: Alignment Mode for DKIM. Allowed values: ‘r’ (Relaxed) or ‘s’ (Strict).

aspf: Alignment Mode for SPF. Allowed values: ‘r’ (Relaxed) or ‘s’ (Strict).

ri: reporting interval for aggregate XML reports in seconds. Example: ri=86400 – 24 hours, ri=3600 – 1 hour. Normally ISP send DMARC reports daily, but they can send them on different intervals.

Examples of DMARC records:

v=DMARC1;p=none; rua=mailto:dmarc-report@domain.com

v=DMARC1;p=reject;pct=100;rua=mailto:agg-report@domain.com

v=DMARC1;p=reject;sp=reject;pct=50;adkim=r;aspf=r;fo=0;ri=3600;
rua=mailto:dmarc-report@domain.com

v=DMARC1;p=quarantine;pct=100;adkim=r;aspf=r;rua=mailto:agg-report@domain.com;
ruf=mailto:for-report@domain.com

Strengthen Your Policy Slowly

We strongly recommend that you ramp up your level of protection using DMARC slowly by employing the DMARC policies in this order.

Start with the “none” policy to collect information about your sending streams and authentication data. Analyze the reports and look for anomalies such as an abnormally high number of sending sources and not signed messages which are probably being spoofed.

When you identify and delete all illegal mail streams and make sure that legitimate senders pass SPF, DKIM and DMARC checks, change the policy to “quarantine”.

Again, monitor the results. When you are absolutely certain that all of your messages are signed, change the policy to “reject” to add the highest level of protection. Check the reports regularly to ensure everything is going well.

Similarly, you can use the optional “pct” tag to increase and test your DMARC deployment. This setting works with the “quarantine” and “reject” policies. Start with a low percentage and increase it every few days.

So, the full DMARC deployment process could be like this:

Day 1 – monitor all.
Day 20 – quarantine 1%.
Day 23 – quarantine 5%.
Day 26 – quarantine 10%.
Day 30 – quarantine 25%.
Day 35 – quarantine 50%.
Day 50 – quarantine all.
Day 60 – reject 1%.
Day 65 – reject 5%.
Day 70 – reject 10%.
Day 75 – reject 25%.
Day 80 – reject 50%.
Day 100 – reject all.

Always, review your daily reports to notice any abnormal behavior and fix the issue.

5. DMARC Monitor

To create a DMARC record and get the DMARC reports, you can use the GlockApps DMARC Monitor.

The GlockApps DMARC Monitor will parse aggregate and forensic reports and present you the valuable data about your email traffic in a comprehensive and user-friendly format.

You can activate the 14-day trial of the DMARC Monitor in your account.

If you don’t have an account with GlockApps yet, you can create a free account here.

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