Why DMARC p=reject Saves MSPs From Blame

Introduction

"Why are our emails broken? What did you change?"

Every Managed Service Provider (MSP) has been there. Your client hired a web developer who decided to send emails from their domain without telling anyone. Now the customer is missing sales leads, and somehow it's your fault.

Here's why DMARC p=reject policies actually protect you from these situations better than p=quarantine - and make your life easier when shadow IT inevitably happens.

The Quarantine Problem: You Get Blamed Anyway

Some DMARC guides tell you to use p=quarantine because it's "safer." But when a web developer or marketing consultant starts sending unauthenticated emails from your client's domain, those emails end up in junk folders.

What happens next:

• Client calls angry about vague "email deliverability issues"
• You spend hours or days investigating
• Complaints pile up about missing communications
• Client assumes you broke something with the email setup
• You're troubleshooting phantom problems while the real culprit sends more mail

The real problem: p=quarantine creates ambiguity. Is it a configuration issue with legitimate senders? A deliverability problem? Or unauthorised sending? You can't tell without deep analysis.

p=reject: Clean Failures, Clear Accountability

With p=reject, unauthorised senders fail immediately and completely. No emails delivered, no junk folders, no confusion.

When that web developer tries sending from your client's domain:

Real-World Example: The Marketing Agency Surprise

The setup: Professional services client with Microsoft 365, properly configured DMARC p=quarantine policy.

What happened: Client's web developer setup a new contact form on their website sending sales leads from their domain to internal staff through a third-party platform - without telling anyone.

p=quarantine result:

• Web sales leads went unnoticed in junk folders
• Client found them one day
• Client called MSP angry about missing sales leads
• MSP spent hours investigating
• Eventually discovered these were unauthenticated from their website contact form
• Still had to explain to the client why some emails worked and others didn't
• On the back foot trying to remediate the issue with the web developer

What p=reject would have done:

• Contact form submissions would have bounced immediately
• Web developer would have contacted client about email failures
• Client would have enagaged MSP to resolve
• MSP could suggest sending these internal messages from a domain the web developer controls

The Shadow IT Reality Check

MSPs deal with shadow IT constantly:

• Web developers sending contact form emails
• Consultants using domain for email campaigns
• Staff signing up for SaaS tools that send notifications
• Accounting software configured by bookkeepers
• HR platforms set up without IT involvement

‍With p=quarantine: Shadow IT mail accumlates in junk folders until someone notices and reports it.

With p=reject: Shadow IT senders fail fast and contact the client to fix authentication.

New Sender Compliance Report Makes p=reject Practical

The traditional argument against p=reject was "you might block legitimate senders by accident." But with tools like VerifyDMARC's Sender Compliance Report, you can see all senders and their overall compliance across all domains.

Instead of clicking through individual domain reports:

• See every sender's compliance status in one view
• Identify authentication gaps across your entire client base
• Apply proven configurations from similar setups
• Monitor p=reject confidently knowing all legitimate senders are covered

Use No DKIM Senders Report

Correctly configured DKIM is important with p=reject policies as some types of mail cannot pass SPF checks. VerifyDMARC's No DKIM Senders report makes it easy to identify legitimate senders that have passed SPF checks but do not have DKIM correctly enabled.

The Business Case: Fewer Support Tickets

p=quarantine support flow:

1. Client reports delivery issues
2. You investigate legitimate email systems
3. You check spam folder placement across providers
4. You analyse DMARC reports for anomalies
5. You discover an new unauthorised sender
6. You explain complex authentication concepts to client
7. You coordinate with client to fix third-party authentication

p=reject support flow:

1. Third-party contacts client about bounced emails
2. Client forwards bounce message asking for help
3. You see "authentication failed" error immediately
4. You provide SPF/DKIM setup instructions
5. Problem solved in one email exchange

What if I am just starting my DMARC journey?

If an existing domain does not have a DMARC policy yet or has a p=none policy with no reporting (rua), setup a p=none policy with a reporting service like VerifyDMARC.

Collect and analyse multiple weeks of reports to ensure all legitimate mail is properly authenticated with SPF and DKIM before moving to a p=quarantine policy, then move to a p=reject policy soon after if no issues are reported.

The Bottom Line

p=reject doesn't just provide better security—it provides better business protection for MSPs. When unauthorised senders fail cleanly, you're not the first person clients call about email problems.

Your clients get clear outcomes: email either works perfectly or fails with obvious error messages. No gray areas, no spam folder investigations, no lengthy troubleshooting sessions for problems you didn't create.

Ready to stop getting blamed for shadow IT email problems?‍

VerifyDMARC's Sender Compliance Report gives you the visibility to deploy p=reject policies safely across all client domains.

See every sender's authentication status in one place and implement policies that protect both your clients and your sanity.

Start your 30-day free trial and experience how p=reject actually makes client management easier.

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