Why email encryption fails when it isn’t cross-platform

Technical interoperability problems appear when different email clients and servers attempt to talk to each other using protocols that are not compatible. Systems built around S/MIME, for example, collide with PGP, leading to failed exchanges or silent fallback to unencrypted delivery. The study ‘Do data security measures, privacy regulations, and communication standards impact the interoperability of patient health information? A cross-country investigation’ found that access control measures, while bolstering security, correlate with 44% higher odds of TI issues. 

Data ends up travelling in the open simply because two platforms can’t agree on how to secure it. Regional rules create semantic and organizational problems, with an 85% in semantic issues and a 76% increase in organizational ones. Many hospitals run multiple EMR systems that exchange protected health information (PHI) via email. The study notes that multi-system environments face 53% higher technical risks and 43% greater semantic breakdowns. The same pattern plays out in common email setups where providers like Microsoft 365 or Google Workspace quietly downgrade to cleartext when the receiving server can’t meet encryption requirements.

Without shared standards, encryption isn’t exchanged or verified across domains. That opens the door to PHI theft, especially in workflows that rely on automatic routing. Platform silos stop keys from being validated or decrypted. 

Why email ecosystems aren’t uniform 

Email ecosystems like Google and Microsoft support different encryption technologies and implement them in uneven ways. Major methods like PGP, S/MIME, and pEp take very different approaches to client compatibility. S/MIME appears in many email clients but depends on certificates from trusted authorities. PGP requires users to create and exchange keys and comes with the need for plugins to work at all times. pEp simplifies these steps but lacks broad support across clients. 

The review ‘Interoperability of heterogeneous health information systems: a systematic literature review’ makes the point clearly: “HL7 FHIR, CDA, HIPAA and SNOMED-CT, SOA, RIM, XML, API, JAVA and SQL are among the most important requirements for implementing interoperability,” and email ecosystems reflect this when they try to reason with incompatible encryption standards.

Setup requirements can create persistent usability problems that create a burden that prevents people from using encryption consistently. Many users don’t know the options exist or abandon them because the tools feel too complex. Outlook and Gmail reflect a pattern. Both need plugins for some encryption methods or offer native support. 

The reason mobile access shapes success 

One BMC Health Services Research study found that 70% of physicians share their mobile numbers with patients and rely on phones with email for updates. When an encryption tool requires Chrome or Edge on a desktop, it breaks that workflow immediately. Browser-specific plugins or portal logins cannot run inside native apps like Gmail, Outlook Mobile, or iOS Mail, which means the message arrives but cannot be opened.

In the medical field, professionals check mobile email constantly for PHI, patient updates, and urgent alerts. When a message can’t be decrypted on a phone, a nurse in transit or a physician on rounds must postpone the task until they can reach a desktop. That delay affects care. Encrypted emails that sit unopened in mobile apps often lead to insecure forwards or ignored alerts, creating situations that increase the risk of HIPAA violations and missed clinical information.

See also: What is HIPAA's encryption and decryption standard?

When encryption becomes too hard to use 

Email is hard to use when users face public key management and setup processes. Research titled ‘Usability of Encryption in E-Mail Communication’ shows that over 60% of participants were unaware of PGP, S/MIME, or pEp technologies and had never tried them, with key generation, exchange, and verification tasks proving excessively burdensome. 

During user testing with 12 participants, struggles peaked when configuring encryption in email clients, as mismatched key strategies (e.g., PGP's web of trust vs. S/MIME's trusted authorities) led to errors and frustration, rendering systems ineffective for daily communication.​

This threshold hits hardest for non-experts, where the difficulty of completing a task exceeds practical limits. Fewer interactions mean higher success, but encryption demands pre-configuration overload, causing 66% of users to abandon it despite concerns like 78% fearing identity theft. 

How platform restrictions break email itself

Client-specific limits, like Gmail’s partial PGP support or Outlook’s dependence on S/MIME certificates issued through Microsoft’s ecosystem, block smooth key exchange across platforms. In their testing for ‘Usability of Encryption in E-Mail Communication’, 70% of users failed basic decryption tasks because plugins were incompatible or because native mobile apps could not handle the encryption at all. When that happens, secure intent collapses into plaintext fallbacks, which undermines email’s open-protocol foundation and exposes PHI in healthcare communication.

These restrictions become even more disruptive when messages move between platforms. Google Workspace pushes users toward browser-based portals for advanced encryption, while Microsoft’s Edge dependent flows prevent decryption in iOS Mail or Android Gmail. Users receive messages they cannot open and often forward them insecurely to access the content. Clinicians cannot read encrypted alerts on native apps

Security risks created by non–cross-platform tool

Hospitals juggle hundreds of disparate applications, devices, and platforms lacking uniform security interfaces, which provides exposure to ransomware and privacy breaches when encryption fails across silos. Without secure interoperability, non-standard tools enable systemic vulnerabilities. Mismatched protocols allow hackers to exploit gaps, blocking IT systems or stealing PHI via portable devices connected to networks, as seen in radiology report compromises.​

One review ‘AI-Induced Cybersecurity Risks in Healthcare: A Narrative Review of Blockchain-Based Solutions Within a Clinical Risk Management Framework’ captures the broader stakes clearly: “The thematic analysis highlighted recurring critical issues: difficulties with informed consent, unauthorized access to sensitive data, and systemic vulnerabilities in hospital digital infrastructures.”

These risks intensify with obsolete software and human errors, where proprietary encryption (e.g., vendor-locked S/MIME) prevents key sharing, leading to plaintext fallbacks and identity theft. Blockchain is proposed for mitigation via immutable logs and protocol enforcement. In unique ecosystems, the absence of cross-platform harmony undermines HIPAA, creating re-identification fraud and single-point failures that jeopardize patient safety.

What cross-platform encryption should look like

A protocol-agnostic model that pairs inbound scanning with AI-driven threat tools and attribute-based encryption (ABE). Instead of relying on user-managed keys, the system assigns access based on attributes allowing encrypted messages to move freely across Outlook, Gmail, and mobile apps without plugins or pre-shared certificates. 

Paubox fits naturally into this direction because it delivers HIPAA-compliant, zero-friction encryption that works behind the scenes, giving organizations the same no-keys, no-plugins experience that ABE architectures aim to standardize.

The approach it encrypts eHealth data at the column level and partitions public keys dynamically, so physicians can decrypt PHI on any device in a secure, consistent way. According to ‘Secure Collaborative Platform for Health Care Research in an Open Environment: Perspective on Accountability in Access Control’, “the HBDP uses attribute-based encryption to achieve fine-grained access control and encryption of stored eHealth data in an open environment.” 

Generative AI expands this interoperability by scanning attachments and message content for threats before delivery, avoiding failures common in PGP or S/MIME exchanges. Tools like pEp introduce auto-key extraction as a first step toward effortless encryption. 

See also: HIPAA Compliant Email: The Definitive Guide (2025 Update)

FAQs

Are browser-based encryption tools compatible across platforms?

Compatibility is limited. Some encryption tools require specific browsers, often Chrome or Edge, and do not work in Safari or Firefox.

Does transport encryption (TLS) fix cross-platform issues?

TLS protects email in transit but does not secure the message end-to-end. If a platform uses outdated TLS versions or accepts self-signed certificates, the connection may be downgraded or intercepted.

Do Gmail and Outlook scan encrypted attachments for threats?

Not always. Some client-side encryption models skip malware scanning because the provider cannot view the contents.