What Is a URI (Uniform Resource Identifier)?

What is a URI?

A Uniform Resource Identifier (URI) is a standardized string of characters used to identify a resource, such as a file, web page, email address, or service, on the internet or a private network. You can think of it as a digital “name tag” that tells systems exactly where to find or reference something.

Every URI follows a specific format defined by the Internet Engineering Task Force (IETF). This format ensures that browsers, email clients, and other software can interpret the same identifier consistently.

A typical URI includes:

For example:

https://dmarceye.com/glossary/uri

Here:

• Scheme: https (defines how to access the resource)
• Authority: dmarceye.com (identifies the host or domain)
• Path: /glossary/uri (specifies the location of the resource)

URIs are the foundation of communication on the web - and by extension, within email protocols, DNS lookups, and authentication frameworks like DMARC.

How Do URIs Work?

When a URI is used, software interprets its components to locate or act upon the resource it describes. Depending on the scheme, a URI might point to:

• A webpage (https://example.com)
• An email address (mailto:support@example.com)
• A file on a server (ftp://files.example.com/report.csv)
• An object in a directory service (ldap://directory.example.org)

In email authentication systems, URIs frequently appear in policy records and reporting mechanisms:

• In a DMARC record, the rua and ruf tags use mailto: URIs to specify where to send aggregate or forensic reports.
• A TLS-RPT record includes a URI to define where Transport Layer Security reports should go.
• Even DNS-based protocols like MTA-STS rely on URIs to describe policy endpoints or reporting addresses.

URIs must always be properly formatted and encoded, since a single missing character or syntax error can cause automated systems to reject a record or fail to deliver reports.

Why URIs Are Important to Email Authentication

URIs are critical for how email authentication protocols communicate between domains. They define where and how to exchange trust information, reports, and policies.

For example:

• A DMARC aggregate report URI (e.g., mailto:dmarc-reports@example.com) ensures visibility into how your domain’s messages are handled across the internet.
• A TLS-RPT URI (e.g., mailto:reports@example.com) helps monitor encrypted mail delivery.
• Even within SPF and DKIM documentation, URIs often describe references to record lookups or public key endpoints.

Because URIs bridge different systems (DNS, SMTP, HTTP), they must remain accurate and up to date. If a URI in your DNS record points to a dead inbox or a misconfigured server, you’ll lose visibility, potentially missing out on critical insights into phishing attempts or delivery issues.

URI and DMARCeye

DMARCeye automatically parses and analyzes URIs found in your domain’s DMARC and related policy records. By examining rua and ruf URIs, DMARCeye helps you:

• Confirm that your reporting addresses are valid and secure.
• Detect issues like malformed URIs or unreachable destinations.
• Visualize which domains your DMARC reports are sent to, helping prevent data leakage to unauthorized third parties.

In essence, DMARCeye turns what might seem like a simple text string (a URI) into a key part of your organization’s visibility and compliance strategy.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.