Interoperability in Electronic Registry Services

What Interoperability Means in Electronic Registry Services

Interoperability is one of the pillars of the new eIDAS 2.0 framework. Its goal is for electronic registry services —which enable certification of digital communications and deliveries with legal validity— to be able to communicate with each other and mutually recognize each other across the European Union.

In practical terms, it means that a certified communication sent from a trusted provider in Spain could be received and verified by another provider in France or Germany with the same legal validity.
A key step toward a single European market for trust services.

QERDS: Technical Interoperability, but with Greater Complexity

The new Regulation introduces the obligation of interoperability between qualified electronic registered delivery services (QERDS). These must adopt common technical protocols and standardized evidence formats, defined by ETSI EN 319 522 and 523 standards, to ensure compatibility between providers across Europe.

However, achieving this interoperability entails greater technical and operational complexity:

• Use of qualified certificates and secure devices.
• Requirements for strengthened identification and authentication.
• Controlled infrastructures between qualified providers.

These requirements provide a high level of legal guarantee, but also increase friction and costs. For this reason, QERDS are more suitable for institutional environments or maximum legal requirements, such as public administrations or notarial procedures.

ERDS: The Effectiveness and Agility Driving Real Digitalization

Electronic registered delivery services (ERDS) —such as eEvidence’s certified email— maintain their full legal validity under Article 43 of Regulation eIDAS, as long as they certify:

• The origin of the sending.
• The complete content of the message.
• The delivery or availability to the recipient.

Unlike QERDS, ERDS do not need to interoperate between providers, since they communicate directly with standard mail servers (Gmail, Outlook, corporate servers, etc.). This makes them more agile, economical, and easy to integrate into any business environment.

In practice, ERDS have become established as the most efficient and widely adopted solution for certifying notifications, claims, contractual communications, or automated processes.

What Changes (and What Doesn’t) with eIDAS 2.0

With the new regulation:

• QERDS will be required to guarantee cross-border interoperability between qualified providers.
• Non-qualified ERDS will continue to have full legal validity, without being subject to this obligation.
• Both models are consolidated as complementary, not competitive.

In short, eIDAS 2.0 strengthens the European ecosystem of trust services, combining interoperability for qualified services with the flexibility and efficiency of non-qualified services.

The Role of eEvidence

eEvidence operates as an electronic registered delivery service (ERDS) registered in the list of the Ministry for Digital Transformation and Public Administration (Spain), in accordance with Regulation (EU) No 910/2014 (eIDAS), offering complete technical and legal proof of the sending, content, and delivery of an email.
Each certified communication generates an evidence document (the eEvid) with:

• Advanced digital signature.
• Qualified timestamp.
• Verifiable cryptographic fingerprint.

Thanks to this architecture based on standard email, eEvidence combines legal security, technical traceability, and ease of integration via API, without requiring complex qualified infrastructures.

Conclusion

The interoperability defined in eIDAS 2.0 represents an advance for qualified services that must exchange evidence on a European scale. However, the simplicity, speed, and effectiveness of ERDS based on certified email will continue to make the difference in the digitalization of business communications.

While QERDS guarantee the connection between trusted providers, ERDS like eEvidence continue to be the most practical and widely adopted tool for secure, traceable, and legally valid electronic communications.