Trust is the modern-day currency of digital communication. Organizations spend years building frameworks to verify identity across websites, applications, and devices. Certificates confirm that a website is who it claims to be. Encryption protects data in transit. Multi-factor authentication verifies users before granting access.

However, there's still a gap. 

Email (the most common business communication channel) often operates without the same standards. And attackers have noticed.

Impersonation attacks continue to rise because sender identity is frequently unverified. Someone claims to be your CEO, your vendor, or your bank. The email looks legitimate. The domain appears correct. But no one actually checked whether the sender was authorized to use that domain in the first place.

Sender identity is the missing layer in many organizations' digital trust posture. Below, we’ll look at what it means, why it matters, and how to close the gap.

Digital trust has a sender problem

Digital trust frameworks have matured over the past decade. Organizations now expect verified identity at almost every digital touchpoint. 

You wouldn't trust a website without a valid certificate, and you wouldn't grant system access without verifying the user. Yet most organizations accept email at face value.

That's a problem, because email is where attackers focus their efforts. 

The FBI's Internet Crime Report found business email compromise (BEC) attacks accounted for over $2.7 billion in reported losses in 2024 alone. Phishing remains the most common initial attack vector for data breaches. And the majority of these attacks rely on one simple exploit: the sender isn't who they claim to be.

The issue isn't that organizations don't care about email security. Most have invested in secure email gateways, spam filters, and employee training. But these defenses focus on detecting malicious content or suspicious behavior. 

They don't verify sender identity at the domain level. That's where the gap lives.

What is sender identity?

Sender identity is the verified answer to a simple question: who is actually sending this email?

When you receive an email that appears to come from your bank, sender identity verification confirms whether the message genuinely originated from an authorized source or whether someone is impersonating that domain. It's the difference between trusting a name on a screen and trusting a cryptographically verified assertion.

The challenge is that email wasn't built with authentication baked in. The protocols that power email were designed decades ago, when trust was assumed, and bad actors were rare. Anyone can send an email claiming to be anyone else. The "From" field is just text.

To fix this, the industry developed a set of authentication protocols: 

• SPF (Sender Policy Framework)

• DKIM (DomainKeys Identified Mail)

• DMARC (Domain-based Message Authentication, Reporting, and Conformance)

Together, these protocols establish sender identity by verifying that an email actually came from an authorized server and that the message wasn't altered in transit.

Just as a TLS certificate verifies that a website is operated by the organization it claims to represent, DMARC verifies that an email is sent by an authorized source on behalf of the domain it claims to come from.

How DMARC establishes sender identity

DMARC is the enforcement layer that ties SPF and DKIM together:

1. SPF specifies which servers are authorized to send email on behalf of a domain. When an email arrives, the receiving server checks whether the sending IP is on the approved list.
2. DKIM adds a cryptographic signature to outgoing messages. The receiving server retrieves the public key from DNS and verifies that the signature is valid and the message wasn't tampered with.
3. DMARC checks whether SPF or DKIM passed and whether the results align with the domain in the visible "From" address. If authentication fails, DMARC tells the receiving server what to do: deliver the message anyway (p=none), send it to spam (p=quarantine), or reject it outright (p=reject).

The main distinction is enforcement. 

A domain with DMARC at p=none is monitoring, not protecting. The domain owner receives reports about authentication failures, but fraudulent emails still get delivered. Only at quarantine or reject does DMARC start to block unauthorized senders.

DMARC also provides visibility. Aggregate reports show every IP that attempts to send email using your domain, whether authorized or not. This visibility helps with identifying shadow IT, misconfigured services, and active impersonation attempts.

Zero trust principles applied to email

The core principle of zero trust is simple: never trust, always verify. 

Every access request is authenticated and authorized, regardless of where it originates.

Sender identity verification applies this same principle to email. Instead of assuming an email is legitimate because it appears to come from a trusted domain, you verify that the sender was authorized to use that domain. Trust is established through authentication and never assumption.

This approach complements existing email security investments rather than replacing them. Secure email gateways analyze content, links, and attachments to detect threats. They use machine learning and threat intelligence to identify suspicious patterns. This is valuable work, but it's fundamentally probabilistic. SEGs essentially make educated guesses about whether an email is malicious.

Sender identity verification is deterministic. Either the sender is authorized, or they aren't. Either DMARC passes, or it fails. 

There's no guessing involved.

Both approaches are necessary. SEGs catch threats that slip past authentication. DMARC stops impersonation at the source. A complete email security posture includes both detection and verification working together.

Why sender identity matters now (more than ever)

Several forces are converging to make sender identity verification more urgent than ever.

• Mailbox provider requirements: Google, Yahoo, and Microsoft now require bulk senders to implement SPF, DKIM, and DMARC. Organizations that don't comply risk having their emails blocked or sent to spam. What was once a best practice is now a baseline expectation.

• Regulatory pressure: Industries with strict compliance requirements are looking at email authentication as part of their security controls. DMARC enforcement demonstrates a commitment to protecting customers and partners from impersonation.

• Brand protection and BIMI: Brand Indicators for Message Identification (BIMI) lets organizations display their logo next to authenticated emails in supported inboxes. But BIMI requires DMARC at enforcement. Organizations that want the visibility and trust benefits of branded email must first verify sender identity.

• Attack sophistication: Impersonation attacks have become harder to detect through content analysis alone. Attackers use clean language, legitimate-looking templates, and well-crafted scenarios. When the content looks normal, the sender identity is often the only signal that something is wrong.

Organizations that don't address sender identity face a growing set of risks: deliverability problems, brand damage, compliance gaps, and successful attacks that bypass content-based defenses.

How to close the gap in your trust posture

The goal is to treat sender identity with the same rigor you apply to other forms of digital identity. Just as certificates verify websites and credentials verify users, DMARC verifies email senders. All three are essential to a complete digital trust posture.

Here’s a methodical approach to closing the gap:

1. Audit your domains. Identify every domain your organization owns, including parked domains and legacy assets. Attackers often target domains that organizations have forgotten about.
2. Implement SPF and DKIM. Configure these protocols for every domain and every service that sends email on your behalf. This includes marketing platforms, CRMs, ticketing systems, and any other third-party senders.
3. Publish a DMARC record. Start with p=none to gather data without impacting email delivery. Review your aggregate reports to understand who's sending as your domain.
4. Move toward enforcement. Once you've authorized all legitimate senders, shift your policy to quarantine and eventually reject. This is where DMARC starts protecting your domain.
5. Monitor continuously. Sender identity isn't a one-time project. New services get added, configurations drift, and attackers adapt. Ongoing monitoring ensures your authentication stays current.

Build trust across every channel

Digital trust is only as strong as its weakest link. Organizations that have invested heavily in securing web traffic, endpoints, and user authentication can't afford to leave email unverified.

Sender identity closes that gap.

The principles are the same across every channel: verify identity, enforce policy, and monitor continuously. Whether you're issuing a certificate or publishing a DMARC record, the goal is to guarantee that digital communications can be trusted.

For organizations ready to take the next step, resources are available to help:

• DMARC-as-a-service solutions for automated enforcement

• BIMI implementation for brand visibility

• Identity assurance frameworks to connect email authentication to your broader trust strategy

Sender identity isn't a nice-to-have. It's the foundation of trusted email communication. And in 2026, trusted communication is the foundation of everything else. 

Take the first step toward verified sender identity. Sign up for Valimail Monitor for free and see exactly who's sending as your domain.