API vs SMTP for secure healthcare emails

Simple Mail Transfer Protocol (SMTP) has been around for decades and was built to move email between servers using a series of text-based commands. It’s reliable and supported almost everywhere, which is why it has remained the backbone of email delivery since the early days of the internet. But its design is basic and linear, so sending messages happens step by step and can be slower. It works well for straightforward email transmission, especially in older systems that still depend on it.

Its staying power in healthcare is also tied to the sector’s historically cautious approach to new technologies. As one Cochrane Library review noted, “The healthcare sector has been more cautious in accepting [email]” compared to industries like banking and insurance. Even though “90% of Internet users [are said] to use email,” healthcare has lagged behind broader adoption.

Email Application Programming Interfaces (APIs) take a very different approach. Instead of relying on server-to-server relaying, APIs connect directly to an email provider’s backend using HTTP requests, like REST calls. This allows emails to be sent faster and with far more flexibility. The tradeoff is that APIs typically require some technical implementation, while SMTP is easier to plug into existing setups because of its long history and compatibility.

In healthcare environments, both methods are still used. SMTP remains common because it integrates easily with long-standing hospital information systems and EHR platforms. It handles routine communications like appointment reminders and basic notifications and works well across different vendors and institutional networks. 

The review found that “nearly two-thirds (64%) were using email to contact other healthcare professionals,” a reflection of how embedded email is in clinical workflows. However, adoption has not always translated into impact. Despite growing interest, “only one study” met the criteria for evaluating how email affects communication among providers. 

It showed that physicians who received email reminders were “more likely to provide guideline‐recommended osteoporosis treatment,” although authors noted the overall impact on patient behavior was mixed and acknowledged “a lack of evidence for the effects of healthcare professionals using email to communicate with each other.”

What SMTP does in healthcare email

While SMTP itself isn’t designed with security or content management in mind, most healthcare systems layer it with encryption, access controls, and other compliance tools to meet HIPAA and internal policy requirements. It is embedded in daily workflows. In a randomized trial of a triage-based email system involving 3,007 patient–physician messages collected over 11 months, SMTP served as the core transport mechanism for communication. 

The study found that 82.8% of messages focused on a single issue, and the most common message types were health updates (41.4%), prescription renewals (24.2%), and health-related questions (13.2%), all categories that align strongly with everyday clinical workflows.

The messages were not only appropriate but manageable. Researchers noted that messages were “concise, formal, and medically relevant,” and less than half (43.2%) required a physician response. The triage model ensured that clinical staff filtered and routed messages so providers only addressed cases that truly needed their attention. 

This allowed nurses and administrative teams to handle scheduling, follow-ups, and routine refills while physicians remained informed without being overwhelmed. The study concluded that “a triage-based e-mail system promoted e-mail exchanges appropriate for primary care” and that physicians’ fears about being flooded with irrelevant or sensitive messages were largely “unwarranted.”

Even though SMTP is an older protocol, it provides a common standard that allows different healthcare systems and vendors to communicate without compatibility issues. Since it doesn’t include built-in encryption or authentication, healthcare organizations typically secure it with TLS or route it through encrypted gateways and secure email services to protect PHI in transit.

How APIs work for email 

APIs make it possible for developers to create tailored email workflows and automate messaging with ease. Instead of operating at the transport level like SMTP, APIs work at the application layer and typically use RESTful HTTP requests to handle tasks such as composing messages, sending them, tracking status, managing inboxes, and attaching files. 

This architecture is better suited for modern security demands because it allows tighter integration with monitoring tools, encryption services, and policy enforcement. The need for this kind of sophistication has only grown in the wake of global digital threats. As a Computational Intelligence and Neuroscience study titled ‘An Advanced Deep Attention Collaborative Mechanism for Secure Educational Email Services’ explains, “The rapid and violent digital transformation [during COVID-19]” exposed entire sectors to “a massive wave of sophisticated and persistent cyberattacks,” especially as services moved online.

When an email API is used, the system receives a request, often in the form of a JSON payload or URL, that includes the relevant details: sender and recipient addresses, subject, message body (in text or HTML), attachments, and any tags or metadata. The provider’s backend then processes the request based on its security policies, business logic, and compliance rules, and sends the message using underlying transport methods, which may still rely on SMTP behind the scenes.

A major advantage of APIs is the feedback they return. They don’t just accept a message and move on; they provide a response confirming whether the send was successful and can supply real-time updates like delivery status, bounce notices, or read receipts. For healthcare organizations, this kind of visibility supports audit trails, message tracking, and overall HIPAA compliance in ways traditional protocols can’t match.

Comparing API and SMTP for email security 

SMTP typically relies on hop-by-hop encryption like TLS, but protection ends once a message reaches the recipient’s inbox. Without true end-to-end safeguards, emails can still be exposed through interception, phishing attempts, or unauthorized mailbox access. If TLS isn’t properly enforced, messages may be vulnerable to man-in-the-middle attacks during transmission. 

According to a Sensors study, the risk is amplified by the fact that phishing remains “one of the most dangerous attacks targeting individuals, organizations, and nations,” and email is still the most common attack vector.

Security also depends heavily on correct server setup, and misconfigurations are a common source of data exposure. In healthcare, these weaknesses increase the risk of violating HIPAA requirements and unintentionally leaking PHI. To compensate, providers often stack SMTP with secure email gateways, third-party encryption tools, and stricter authentication controls to stay compliant and mitigate risk.

API-based email security frameworks operate differently. Instead of protecting only the transit layer, they plug directly into cloud platforms like Microsoft 365 and Google Workspace using native APIs. This deeper integration gives continuous visibility into mailbox activity and message content after delivery. It also enables real-time threat detection that SMTP alone can’t offer. 

By tracking communication patterns and user behavior, API-driven systems can flag subtle signs of phishing, account takeover, or insider misuse. Advanced detection models are making a measurable difference. The study found that augmented deep learning approaches, specifically a 1D-CNNPD model with Bi-GRU, achieved 100% precision, 99.68% accuracy, and an F1 score of 99.66% when identifying phishing emails. The authors concluded that “these models can advance the implementation of cybersecurity solutions to combat email phishing attacks” and reduce reliance on manual detection methods.

The requirements for a HIPAA-compliant email transmission

• Any email that includes PHI needs to be encrypted, both while it’s being sent and while it’s stored, so unauthorized parties can’t access it.
• The email provider has to sign a BAA with the healthcare organization and take on shared responsibility for protecting PHI.
• Access to email accounts should be tightly controlled with strong passwords and multi-factor authentication, making sure only approved staff can log in.
• Secure transmission protocols like TLS 1.2 or higher must be used so data stays protected while it’s in transit.
• HIPAA compliant email systems need to keep detailed logs of who accessed, sent, or received messages containing PHI so there’s a clear record for audits and investigations.
• Organizations should have administrative safeguards in place, including written email policies, regular risk assessments, and staff training on secure email practices.
• Patients should give documented consent before receiving PHI electronically.
• Emails that contain PHI must be stored securely and retained for at least six years to meet legal requirements.
• There should be built-in monitoring to catch unauthorized access, suspicious behavior, phishing attempts, and other email threats.
• The email platform should include secure archiving to make sure records remain intact, accessible, and tamper-proof throughout the retention period.

When APIs become more secure than SMTP

APIs offer stronger security than traditional SMTP when email delivery is handled through authenticated, token-based access instead of basic username and password logins. With API keys or OAuth tokens, credentials can be time-limited, tightly scoped, and quickly revoked without interrupting broader systems. Unlike SMTP credentials that are often shared across services, API tokens are tied to specific functions and applications.

Security is also built into the transport layer. Because APIs use secure HTTPS connections, email data remains protected across the entire communication path, not just during transmission between servers. This allows healthcare organizations to restrict access to trusted software components they control. 

The above-mentioned Cochrane study on clinical email communication notes that email in healthcare has historically been underused despite being “one of the most widely used methods of communication,” largely due to concerns around privacy, misuse, and the absence of structured safeguards. APIs directly address these issues with permission granularity that SMTP cannot match.

APIs also bring built-in visibility and security oversight that SMTP simply wasn’t designed for. Instead of just moving messages from one server to another, APIs can monitor emails in real time, watching for phishing behavior, malware, mass sending anomalies, or unusual user activity. 

When something looks off, the system can step in immediately by blocking credentials, isolating messages, alerting security teams, or triggering automated responses. For healthcare environments that need to move quickly to stay HIPAA-compliant and defend against evolving threats, this kind of adaptive protection is a major advantage over the static, transfer-only nature of SMTP.

FAQs

What is email encryption?

Email encryption protects the content of an email so that only the intended recipient can read it. It scrambles the message into unreadable text during transmission and, in some cases, while stored on a server.

Is TLS enough for secure healthcare email?

TLS protects messages in transit, but once a message reaches the recipient’s inbox, it is no longer encrypted. Because of this limitation, TLS alone may not be sufficient for transmitting PHI unless layered with additional safeguards.

Can email attachments be encrypted, too?

Yes. Attachments such as PDFs, forms, and images can be encrypted along with the email body.