Discovering Who's Pointing SPF Records at Your Domain with SPF Macros

Ever Wondered Which Domains Include Your SPF Record?

If you're a SaaS vendor, email service provider, or any organisation whose domain gets included in other companies' SPF records, you've likely asked yourself: "Who exactly is pointing their SPF records at my domain?"

SPF (Sender Policy Framework) allows domain owners to publish a list of IP addresses or subnets authorised to send email on their behalf. When another organisation adds your domain via an include: mechanism, they're essentially trusting your infrastructure to send mail as them. But there's no built-in way to discover the reverse — who's trusting you.

Until now.

The Problem: No Reverse Visibility

Imagine you're vendora.example.com, a company that sends transactional email on behalf of clients. Your clients — let's say example.org — add something like this to their SPF record:

v=spf1 include:vendora.example.com ~all

When someone receives an email from example.org, their mail server checks this record to verify whether the sending server is allowed to act on their behalf. The receiving server follows the include: chain, eventually looking up vendora.example.com's SPF record to check the sending IP.

But as vendora.example.com, you have no native way to see which domains have included you. You might know your customers from your own records, but what about:

• Former customers who never cleaned up their DNS?
• Unauthorised parties referencing your domain?
• Domains you didn't even know about?

The Solution: SPF Macros + spf.guru

SPF records support macros — dynamic placeholders that get expanded at query time by the receiving mail server. Two macros are key here:

Macro	Meaning
%{ir}	The reverse IP address of the connecting (sending) mail server
%{o}	The original domain from the SMTP MAIL FROM (envelope sender)

By cleverly embedding these macros into your SPF record and pointing them at a logging service like spf.guru, you can capture who's including your domain in real time.

How It Works: Step by Step

1 Add the macro to your domain's SPF record

If your domain is vendora.example.com, update your SPF record to include the spf.guru macro:

v=spf1 include:i.%{ir}._d.%{o}.my.spf.guru ~all

(You can add your other mechanisms alongside it, of course.)

2 A client includes your domain

Your client, example.org, has the following in their SPF record:

v=spf1 include:vendora.example.com ~all

3 An email is sent from example.org

When a mail server at IP 203.0.113.42 sends an email with a MAIL FROM of user@example.org, the receiving server performs an SPF check. It:

1. Looks up the SPF record for example.org
2. Sees include:vendora.example.com
3. Looks up the SPF record for vendora.example.com
4. Finds the macro include:i.%{ir}._d.%{o}.my.spf.guru
5. Expands the macros at query time:
   • %{ir} becomes 42.113.0.203 (the reversed IP)
   • %{o} becomes example.org (the original envelope sender domain)
6. Performs a DNS lookup for:

i.42.113.0.203._d.example.org.my.spf.guru

4 spf.guru logs the query

The DNS query hits spf.guru's nameservers, which log the request. Now you have a record showing:

• The sending IP (from %{ir}): 203.0.113.42
• The original domain (from %{o}): example.org
• Pass/Fail result

5 View your results

Visit https://spf.guru to see all logged results, giving you a clear picture of which domains are including your SPF record and which IPs are sending on their behalf.

Why This Matters

This approach gives you powerful visibility:

• 🔎 Discover unknown includers — Find domains referencing your SPF record that you didn't know about.
• 🧹 Identify stale references — Spot former clients who still have your domain in their SPF records.
• 🛡️ Security monitoring — Detect unauthorised use of your sending infrastructure.
• 📊 Audit your footprint — Understand the full scope of your email sending reputation impact.

Important Considerations

⚠️ DNS Lookup Limits: SPF records are limited to 10 DNS lookups per evaluation. The spf.guru macro adds to this count, so make sure your clients' SPF records (and your own) don't exceed this limit.

ℹ️ Macro Support: While SPF macros are part of the RFC 7208 specification, not all receiving mail servers fully support macro expansion. In practice, most major providers do.

• Privacy: Be mindful that you're logging sending IPs and domain names. Make sure this aligns with your privacy policies.
• Response behaviour: The spf.guru service will respond to DNS queries in a way that doesn't break your SPF evaluation — check their documentation for details on pass/fail behaviour.

Quick Setup Checklist

• ✅ Visit https://spf.guru no need to set up an account
• ✅ Add include:i.%{ir}._d.%{o}.my.spf.guru to your domain's SPF record
• ✅ Keep your existing SPF mechanisms (IP addresses, other includes, etc.)
• ✅ Verify the record with an SPF checker tool
• ✅ Monitor the spf.guru dashboard for incoming data

Wrapping Up

SPF macros are an underutilised but powerful feature of the SPF specification. By combining them with a logging service like spf.guru, you gain reverse visibility into your SPF ecosystem — something that's traditionally been a blind spot for email infrastructure teams.

If you're a vendor or service provider whose domain appears in other organisations' SPF records, this simple addition to your DNS can unlock invaluable insights into who's relying on your sending infrastructure.

Stop Bypassing DMARC: A Supply Chain Reality Check

DMARC isn’t the problem—how we respond to failed authentication often is.

TL;DR: Don’t add bypasses when supply-chain email fails DMARC. Report it to the sender and ask them to fix their authentication. Most “legit” failures trace back to shadow IT or unsanctioned senders, not broken DMARC.

For years, organisations have looked at DMARC with a mix of admiration and fear. On one hand, it’s one of the most effective controls to protect customers, partners, and employees from email impersonation. On the other, it’s often blamed for “breaking” legitimate business email.

The truth? More often than not, the problem isn’t DMARC. It’s how we respond when email from the supply chain doesn’t align.

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The Easy Way Out: Adding Bypasses

When an important invoice, purchase order, or system notification is blocked because of DMARC, the reflex in many IT teams is to add a bypass. After all, business continuity matters. The sender insists the mail is “legitimate,” so why not?

Here’s the catch: bypasses introduce risk at scale. Once you start allowing mail that fails authentication, you’re effectively unravelling the very purpose of DMARC—keeping bad actors out of your users’ inboxes.

• Every bypass weakens your email security posture.
• Exceptions pile up and become hard to track or remove.
• Attackers learn to exploit known “allow” paths.

The Perception Problem

There’s a persistent narrative that “lots of organisations mess up their DMARC records” and that this causes widespread delivery issues. While misconfigurations do happen, context is everything:

• If a domain owner sets p=quarantine or p=reject, they’ve made a deliberate risk decision.
• From the outside, you can’t know if the “blocked” email was sanctioned or came from shadow IT—a platform sending on behalf of the organisation without security or data-privacy onboarding.

In other words, what looks like a false positive may actually be a false assumption.

The Shadow IT Grey Zone

This is the greyest of grey areas. That “legitimate” email may be:

• A SaaS tool bought on a corporate credit card.
• A system that never went through a security review.
• An integration no one in IT approved or onboarded.

In many cases, the sender’s own IT and security teams don’t authorise the source. Which means the sender will face the same DMARC “issues” with everyone they email—not just you.

Yes, Edge Cases Exist

Are there times when a sanctioned application has been genuinely missed during onboarding and the sender is enforcing DMARC? Of course. DMARC, like any control, isn’t immune to operational oversights.

But best practice is simple: report the issue to the sending organisation. Let their IT and security teams validate the source, correct SPF/DKIM/DMARC, and update their records accordingly—so the fix scales to all recipients, not just you.

Why This Matters

• Security: Bypasses open doors for spoofing and business email compromise (BEC).
• Consistency: Exceptions create inconsistent delivery and unpredictable support load.
• Scale: Fixing at the sender side benefits every recipient; a local bypass only helps you—and increases your risk.

DMARC is only as strong as the weakest exception.

What to Do Instead (Playbook)

1. Hold the line: Don’t create allow-lists or bypasses for failed authentication.
2. Notify the sender: Share the error and message sample (headers, authentication results).
3. Ask for basics: Confirm the sender’s authorised platforms and whether IT/security sanctioned them.
4. Verify fixes: Look for correct alignment: SPF (envelope/HELO), DKIM (aligned signing domain), and a valid DMARC policy.
5. Close the loop: Test again and remove any temporary, time-boxed mitigations.

Helpful Language for Stakeholders

“We don’t add bypasses for failed DMARC. Please have your IT/security team confirm the sender is authorised and ensure SPF/DKIM align with your DMARC policy. Once corrected, delivery will work for all recipients, not just us.”

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Final Thought

Instead of defaulting to bypasses, flip the script: treat failures as a supply-chain improvement opportunity. Push vendors and partners to properly onboard their sending systems. Recognise that DMARC isn’t the enemy—shadow IT is.

When you protect the integrity of your email channel, you’re not just defending your organisation—you’re raising the bar for everyone in your supply chain.

If you found this useful, consider sharing with your security and procurement teams—DMARC success is a team sport.

What’s a “User-Agent” Anyway?

What’s a “User-Agent” Anyway?

Whenever your web browser, mobile app, or an automated script requests a web page, it quietly introduces itself with a User-Agent header. Think of it as the digital equivalent of saying, “G’day, I’m Chrome on a Windows laptop” when you walk through the door of a website.

Here’s a typical example (no need to memorise it!):

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36

Each chunk tells the server something about the requester:

• Browser / Engine – Chrome/124…
• Operating System – Windows NT 10.0
• Architecture – Win64; x64

Servers use that information to decide which content or layout to send back (for example, a mobile-friendly page for a phone).

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Why Cyber-Security Folks Care About User-Agents

Because the header is just text, any tool can claim to be anything. That makes the User-Agent string both useful and potentially dangerous.

1 · Spotting “Good” Bots vs “Naughty” Bots

Security teams keep lists of known, legitimate scanners—think Microsoft Defender SmartScreen or Google’s Safe Browsing crawler. These bots announce themselves with recognisable User-Agents such as:

• Mozilla/5.0 AppleWebKit/… +https://safebrowsing.google.com/
• Mozilla/5.0 (compatible; MS Defender SmartScreen URL Reputation)

Firewalls and e-mail gateways can then decide, “If it’s that scanning tool, let it through; if it’s something pretending to be Chrome 99 on Windows 95, maybe block or sandbox it.”

2 · Reducing “Single-Click” Mishaps

Imagine you receive an e-mail saying, “Approve expenses by clicking here.” Corporate web-filters might pre-click (or “prefetch”) that link to scan it for malware. That protective click could accidentally approve the request on your behalf if the app trusts the first visitor.

Risky Design	Safer Design
A link that performs a sensitive action via GET (one click)	The link leads to a page that asks for confirmation or a POST/PUT with a CSRF token
No distinction between a user’s browser and an automated scanner	Check the User-Agent (plus IP range, headers, timing) and require a logged-in session

User-Agent alone isn’t fool-proof, but it’s a quick first check—“Does this look like our employee’s browser or a known scanning engine?”

3 · Phishing-Simulation Campaigns

Security-awareness vendors send test phishing e-mails to staff. Their links often record the User-Agent so the report can say:

“Jess clicked on the lure from an iPhone running Safari 17.”

Teams use that data to tune training. For example, if 80 % of clicks came from mobile devices, the next awareness module should highlight mobile red flags.

4 · Incident Response & Threat Hunting

Log files packed with User-Agents help responders answer questions like:

• When did the attacker start probing? – A sudden flood of sqlmap/1.7 strings reveals automated SQL-injection sweeps.
• Which systems are compromised? – Spotting a weird User-Agent beaconing to an external server can help trace infected endpoints.

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How Attackers Abuse the Header

Tactic	Example	Why It Matters
Spoofing	Malware sets its User-Agent to Mozilla/5.0 … Chrome/124…	Blends in with normal traffic to dodge simple filters.
Fingerprinting	Evil site inspects every detail (CPU i686, Locale en-AU)	Builds a unique profile to follow you even without cookies.
Force-Click Exploits	Attacker e-mails a link that auto-approves an action; they rely on corporate scanners hitting it first	The victim’s security tool becomes the unwitting clicker.

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Practical Tips for Beginners

1. Never trust the User-Agent alone. Validate sessions with tokens, CAPTCHAs, or multifactor prompts for sensitive actions.
2. Log it anyway. Even if it can be faked, patterns over time are gold for threat hunting.
3. Sandbox first-click actions. If your mail gateway or browser plugin pre-scans links, ensure downstream apps require an extra confirmation step.
4. Use allow-lists judiciously. Maintain a catalogue of genuine security scanners (Defender, CrowdStrike, Proofpoint, Mimecast, etc.) and apply looser rules only to those User-Agents and their known IP ranges.
5. Stay updated. Browsers are moving towards Client Hints (shorter, privacy-friendly headers). Keep an eye on how your tooling parses those.

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Wrapping Up

The humble User-Agent string is a small line of text that packs a punch. For web developers, it’s a way to serve the right layout; for cyber-defenders, it’s another clue to separate friend from foe. Treat it as a helpful hint, not gospel truth, and combine it with solid authentication and logging. That way, whether it’s a real user approving expenses or a phishing simulator prodding for gaps, you’ll know who’s truly knocking at your digital front door.

Why DMARC Matters: How Modern Email Platforms Enforce It to Stop Spoofing

Email remains the #1 channel attackers abuse for phishing, impersonation and fraud. The industry-standard defence is the trio of SPF, DKIM and DMARC. Domain owners publish the policy, but here’s the crucial bit:

The responsibility for enforcing DMARC sits with the receiving mail servers—and the major cloud platforms already honour DMARC out of the box.

Who Actually Enforces DMARC?

Publishing a DMARC record doesn’t block spoofing on its own. DMARC works when the recipient’s mail system checks and enforces it. That’s exactly what the dominant email platforms do today:

Receiving Platform	DMARC Enforcement	Notes
Microsoft 365 (Exchange Online)	✅ Enabled by default	Built-in SPF, DKIM and DMARC validation on ingress
Google Workspace (Gmail)	✅ Fully enforced	Strict SPF/DKIM checks with DMARC policy honouring
Yahoo / AOL (Verizon Media)	✅ Enforced aggressively	Early DMARC adopters; strong stance against spoofing
Apple iCloud Mail	✅ DMARC-aware	Treats failing DMARC messages as suspicious
Secure Email Gateways (Mimecast, Proofpoint, Cisco, etc.)	✅ Standards-compliant	DMARC checks are table stakes for modern gateways

Practical takeaway: Because most business and consumer mail is received by these platforms, the vast majority of inboxes already enforce your DMARC policy.

Adoption at Scale: Microsoft 365, Google Workspace & Co.

• Microsoft 365 serves hundreds of millions of commercial mailboxes globally. Exchange Online validates SPF/DKIM and enforces DMARC policies by default.
• Google Workspace / Gmail powers more than a billion consumer mailboxes and millions of businesses; DMARC is first-class and strictly applied.
• Other majors (Yahoo/AOL, Apple, Outlook.com) and leading email security providers also honour DMARC by default.

In short, if your organisation emails customers, partners or staff using mainstream providers, your published DMARC policy is being read and enforced at the other end.

What About Legacy or Unpatched On-Prem Mail Servers?

Some legacy on-premises MTAs (e.g. very old Exchange versions or unmaintained open-source stacks) may not fully validate DMARC. However, if a server is so old it can’t honour DMARC, it almost certainly has a long list of other security vulnerabilities—missing patches, weak TLS, outdated auth, and limited phishing controls. These environments are now the exception, not the norm, and most are fronted by secure gateways that do enforce DMARC.

Stopping Spoofing: SPF + DKIM + DMARC

• SPF: Verifies the sending IP is authorised for the domain.
• DKIM: Cryptographically signs the message to prove integrity and domain control.
• DMARC: Ties it together—requires alignment and tells receivers what to do on failure (none, quarantine, reject).

Together, these form the industry solution for eliminating direct domain spoofing across modern inboxes.

Stronger Enforcement in the Last 12–18 Months

Major receivers have tightened the screws:

• Google & Yahoo: Tougher requirements for bulk senders; unauthenticated mail is throttled, spam-foldered, or rejected.
• Microsoft: Increased scrutiny and filtering of non-aligned, non-authenticated messages that attempt domain impersonation.
• All majors: Ongoing nudges towards proper SPF/DKIM/DMARC hygiene, improving safety across the ecosystem.

What This Means for You

• Publish DMARC and aim for p=quarantine or p=reject once you’ve validated legitimate senders.
• Authenticate everything (marketing platforms, CRMs, ticketing tools, finance systems) with SPF and DKIM, aligned to your primary domain or subdomains.
• Monitor reports (DMARC RUA) to see who’s sending with your domain and fix gaps before enforcing.

Because receivers already honour DMARC, setting a strong policy immediately reduces successful spoofing against your brand.

Bottom Line

DMARC isn’t just a DNS record—it’s a powerful instruction that modern mail platforms follow by default. In a world dominated by Microsoft 365, Google Workspace and leading security gateways, SPF + DKIM + DMARC is the proven, widely enforced way to stop direct domain spoofing and protect trust.

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Tip: If you’re still migrating from legacy systems, put a secure email gateway in front—or accelerate your move to cloud email—to ensure DMARC is fully enforced on inbound mail.

Why SPF Soft‑Fail (~all) Is the Smarter Choice for Deliverability

When you publish an SPF record with a hard‑fail (-all), you’re telling every receiver to reject mail from any IP not explicitly authorised. It sounds secure—but it can do more harm than good. In many real‑world scenarios, a soft‑fail (~all) policy delivers the same security under DMARC while avoiding collateral damage to legitimate mail flows. Here’s why staying in soft‑fail often makes the most sense.

1. SPF’s Bypass Vulnerability

SPF checks only the envelope sender (MAIL FROM), not the visible “From:” header. An attacker can exploit this by using a domain they control in the envelope, yet spoof your brand in the header—completely bypassing SPF’s intended protection. DMARC addresses this gap by requiring alignment, but it underscores that SPF alone is never a standalone defence.

2. Under DMARC, “Hard” = “Soft”

Once DMARC is active, any SPF result aside from an aligned “pass” will break SPF alignment—whether it’s -all, ~all or ?all. The receiving system then defers to DKIM or DMARC’s own policy (none, quarantine, reject). In practice, hard‑fail offers no extra benefit under DMARC.

3. The Relaying (Forwarding) Problem

Legitimate forwarding or relaying services—common in multi‑domain setups—break SPF. A forwarded email often arrives from an IP not listed in your SPF, triggering a hard‑fail. With -all, that message is bounced before DKIM or DMARC can save it. Soft‑fail, however, allows the mail through for full authentication checks, ensuring genuine mail survives forwarding.

4. RFC‑Mandated Caution on Early Rejection

The DMARC specification warns that a hard‑fail may cause some receivers to reject mail before DMARC and DKIM can be evaluated. You could lose perfectly legitimate, DKIM‑signed messages simply because SPF blocked them too early.

5. Domain Reputation Isn’t Improved by -all

There’s no evidence that hard‑fail boosts your sending reputation—any “reputation” gain from blocking illegitimate mail is outweighed by the spikes in bounces and NDRs you’ll generate. Soft‑fail avoids those bounces, keeps your bounce rate in check, and still provides the same DMARC‑driven security.

6. Recommended Email Hardening Workflow

1. Publish SPF with ~all to collect data without breaking flows.
2. Deploy DMARC (start with p=none), review reports to identify missing senders.
3. Enable DKIM signing for all legitimate sources and ensure alignment.
4. Tighten DMARC to quarantine or reject once DKIM coverage is 100%.
5. (Optional) Switch SPF to -all only if you’re absolutely certain no valid mail will break alignment.

7. When -all Still Makes Sense

For domains that should never send email—such as parked domains or inbound‑only mailboxes—a hard‑fail SPF aligned with a DMARC p=reject policy is appropriate. But for active sending domains, soft‑fail maximises deliverability without compromising DMARC‑backed security.

Conclusion

SPF hard‑fail is a relic from a pre‑DMARC era. Today, with DMARC and DKIM doing the heavy lifting, soft‑fail (~all) gives you the best of both worlds: visibility into unauthorised flows, robust protection against spoofing, and minimal risk of blocking legitimate mail. Start soft, monitor closely, then only tighten when you’ve seen every source through the lens of DKIM and DMARC.

Navigating the Challenges of Using Distribution Lists with DMARC Enforcement

When managing email infrastructure, ensuring secure and reliable communication is paramount—especially for system administrators, systems engineers, and tech support professionals. One common challenge arises when distribution lists in Exchange are used to forward emails to external recipients, particularly when the original sender’s domain enforces strict DMARC policies. In this post, we dive into the technical challenges and practical solutions to keep your email deliverability on track.

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The Technical Landscape

DMARC, SPF, and DKIM: The Basics

DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) by ensuring that the authenticated domain in the "From:" header aligns with the sender’s policy. For organizations with strict DMARC settings (using policies like reject or quarantine), even small misalignments can result in legitimate emails being blocked or marked as spam.

Distribution Lists in Exchange

Distribution lists simplify communication by allowing you to send one email to multiple recipients. While they work flawlessly within internal networks, issues arise when:

• Recipients are External: Emails forwarded to addresses outside your domain.

• Sender's Domain Enforces DMARC: The original sender’s email is preserved during forwarding, causing potential DMARC failures if the forwarding server isn't authorized in the SPF records.

When the email’s envelope remains unchanged after forwarding, the external server may reject the message if the SPF and DKIM checks don’t pass DMARC validation.

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Key Challenges

DMARC Alignment Failures

When forwarding via a distribution list, the original sender’s "From:" header is maintained, yet the Exchange server’s IP isn’t typically listed in the sender’s SPF records. Without adjustments, this misalignment can trigger SPF failures—and if DKIM is also compromised during the forwarding process, the entire DMARC validation fails.

Impact on Email Deliverability

Strict DMARC policies mean that even legitimate emails can be blocked or quarantined. This disrupts business communications and can hurt the sender's reputation if valid emails never reach their external recipients.

Complex Authentication Chains

Forwarding complicates the authentication process because the original sender’s credentials remain intact, while the message is transmitted via a server that isn’t part of the sender’s authorized network. This leads to a breakdown in the trust chain that DMARC relies on.

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Mitigation Strategies

1. Address Alteration

One effective strategy is to alter the sender’s address during the forwarding process. By rewriting the sender’s address to a domain that is DMARC-compliant (typically the forwarding domain), you ensure that SPF records align and reduce the likelihood of DMARC failure.

Implementation Tips:

• Configure the Exchange server or distribution list to update the envelope sender.

• Use email routing rules to replace the “From:” or envelope sender with an authorized address.

2. Sender Rewriting Scheme (SRS)

SRS is designed to tackle DMARC issues in forwarding scenarios. It rewrites the envelope sender address so that the email appears to originate from a domain authorized to send emails on behalf of the forwarder.

Benefits of SRS:

• Maintains SPF Alignment: Rewrites the sender address to match the forwarder’s SPF records.

• Transparency: Allows traceability back to the original sender, even with the rewritten address.

• Seamless Integration: Can be incorporated into existing Exchange environments with the right configuration.

3. Combined Approaches

In some instances, a hybrid approach using both address alteration and SRS may offer the best results. While SRS tackles the SPF alignment issue, additional measures such as re-signing the email with DKIM on the forwarding server can further secure the forwarded email.

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Best Practices for Email Delivery Professionals

• Regular DMARC Policy Reviews:
  Avoid overly strict DMARC policies on emails that might be legitimately forwarded. Consider starting with a “quarantine” policy to monitor impact before moving to “reject.”

• Monitor with DMARC Reporting Tools:
  Leverage DMARC reports to track authentication failures. This data is invaluable for refining forwarding rules and determining if further adjustments are needed.

• Test Before Deployment:
  Always validate configuration changes (address alteration, SRS implementation) in a test environment to ensure smooth delivery to external recipients.

• Stakeholder Education:
  Ensure that IT, security teams, and support staff understand these changes. Proper documentation and training can help streamline the transition and reduce confusion.

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Conclusion

For professionals managing email delivery, particularly in environments with strict DMARC enforcement, forwarding emails via distribution lists in Exchange can present unique challenges. The crux of the issue lies in preserving the original sender’s details while satisfying DMARC requirements. By employing strategies like address alteration and SRS, you can maintain SPF alignment and safeguard your email communications. These solutions not only enhance deliverability but also ensure robust email security—critical for today’s dynamic email landscape.

Stay tuned for more insights on email delivery, and happy mailing from all of us at Delivery Depot!

DMARC Reports: Debunking Privacy Myths and Minimizing Risk

Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an essential email authentication protocol designed to protect your domain from being used in phishing and spoofing attacks. 

One of DMARC’s core features is its ability to generate reports that provide valuable insights into who is sending emails on behalf of your domain. However, some organizations are hesitant to enable DMARC reporting due to concerns about sharing potentially sensitive data with third parties. This article aims to dispel misconceptions about DMARC reporting, clarify what information is actually shared, and provide practical guidance on how to minimize privacy risks.

Understanding DMARC Reports

DMARC generates two types of reports:

1. Aggregate Reports (RUA) - These reports provide a high-level overview of email authentication results, including metadata such as sending IP addresses, domain alignment, and the DMARC policy applied. They are sent to the address specified in the "rua" tag of your DMARC record.
2. Forensic Reports (RUF) - These reports, also known as failure or message-specific reports, contain more detailed information, including message headers, and in some cases, subject lines and content. They are sent to the address specified in the "ruf" tag.

Who Generates the Reports?

A common misconception is that sending DMARC reports involves your email server transmitting data to third parties. In reality, it is the receiving email server that generates these reports. When your domain sends an email to another server (like Gmail or Outlook), that server checks your DMARC policy and, if configured, generates a report based on the result of that check. Therefore, your organization has no control over whether a receiving server generates these reports once your policy requests them.

Aggregate vs. Forensic Reports

While both report types serve to increase visibility into your domain’s email traffic, they differ significantly in terms of privacy implications:

Aggregate Reports (RUA)

• Generated regardless of DMARC outcome (pass or fail).
• Contain only metadata and no email content, making them relatively safe from a privacy perspective.
• Typically sent daily and in XML format.

Forensic Reports (RUF)

• Generated only when a message fails DMARC checks.
• May include potentially sensitive information, such as message headers and even parts of the email body.
• Not all receiving servers generate forensic reports—many have opted not to, due to privacy and compliance concerns.
• The default behavior is to generate forensic reports only on DMARC failures.

Minimizing Privacy Risks

The best way to mitigate privacy risks is to limit which reports you request in your DMARC policy:

1. Exclude Forensic Reports (RUF) - Simply omit the "ruf" tag from your DMARC record to ensure no forensic data is collected or shared.

   Example DMARC record without RUF:

   v=DMARC1; p=reject; rua=mailto:dmarc-reports@yourdomain.com
   

2. Use Trusted Email Reporting Services - If you do use RUF, consider configuring it to send to a trusted third party or internal system that is designed to securely manage sensitive data.

3. Review Privacy Policies of Receiving Servers - Understand that the vast majority of servers do not generate forensic reports at all, and those that do typically redact or minimize content to protect privacy.

Final Thoughts

For organizations new to DMARC, the potential risks around RUF reports can seem daunting. However, the reality is that the vast majority of DMARC data shared is aggregate metadata that poses little to no risk of exposing sensitive content. By configuring your DMARC record carefully and opting only for RUA reports, you can significantly minimize your privacy exposure while still gaining valuable insights into email authentication.

Have questions or need more guidance on implementing DMARC? Reach out to a trusted expert to ensure your email domain is protected while maintaining privacy best practices.