Proofpoint Secure Email Relay Mail API Java Library

This library implements all the functions of the SER Email Relay API via Java.

Requirements

• Java 11+
• HttpClient (built-in in Java 11+)
• Active Proofpoint SER API credentials

Installing the Package

You can include the library in your project using Maven:

<dependency>
    <groupId>io.pfpt.ser</groupId>
    <artifactId>ser-mail-api</artifactId>
    <version>x.x.x</version>
</dependency>

Features

• Send Emails: Easily compose and send emails with minimal code using a fluent builder pattern.
• Support for Attachments:
  • Attach files from disk
  • Encode attachments as Base64
  • Send byte[] attachments
• Support for Inline HTML Content:
  • Using the syntax <img src="cid:logo">
  • Content-ID can be set manually or auto-generated
• HTML & Plain Text Content: Supports both plain text and HTML email bodies.
• Recipient Management: Add To, CC, and BCC recipients with ease.
• Reply Management: Add Reply-To addresses to redirect replies.

Quick Start

import io.pfpt.ser.mail.*;

public class Example {
  public static void main(String[] args) {
    // Initialize the Client with OAuth credentials from the config
    Client client = new Client("<client_id>", "<client_secret>");

    // Use the fluent builder to construct and send an email
    Message message = Message.builder()
            .subject("This is a test email") 
            .from("sender@example.com", "Joe Sender") 
            .addContent("This is a test message", Content.ContentType.TEXT)
            .addTo("recipient1@example.com", "Recipient 1") 
            .build();
    
    // Send the message asynchronously and wait for the result
    SendResult sendResult = client.send(message).join();
    
    // Output the HTTP status code from the API response
    System.out.println("HTTP Status: " + sendResult.getHttpResponse().statusCode());
    // Output the message ID from the API response
    System.out.println("Message ID: " + sendResult.getMessageId());
    // Output the reason (if any) from the API response
    System.out.println("Reason: " + sendResult.getReason());
    // Output the request ID from the API response
    System.out.println("Request ID: " + sendResult.getRequestId());
  }
}

Advanced Emails

import io.pfpt.ser.mail.*;

public class Example {
  public static void main(String[] args) {
    // Initialize the Client with OAuth credentials from the config
    Client client = new Client("<client_id>", "<client_secret>");
    
    // Construct logo_a attachment with dynamic content ID
    var logo_b = Attachment.builder()
            .fromFile("c:/temp/logo_b.png") // Load logo_b from file
            .dispositionInline() // Set dynamic content ID
            .build();

    // Use the fluent builder to construct the Message in a single chain
    Message message = Message.builder()
            .subject("This is a test email") // Sets the email subject (required)
            .from("sender@example.com", "Joe Sender") // Sets the sender (required)
            .addContent("This is a test message", Content.ContentType.TEXT) // Adds plain text content (required minimum)
            .addContent(// Required: Adds HTML content referencing both static and dynamic CIDs
                    "<b>Static CID</b><br><img src=\"cid:logo\"><br><b>Dynamic CID</b><br><img src=\"cid:" + logo_b.getContentId() + "\">",
                    Content.ContentType.HTML) // Uses logo_b's auto-assigned content ID retrieved from getContentId()
            .addAttachment(Attachment.builder().fromFile("C:/temp/logo_a.png").dispositionInline("logo").build()) // Adds an inline attachment with content ID "logo"
            .addAttachment(logo_b) // Adds logo_b with its dynamically assigned content ID
            .addTo("recipient1@example.com", "Recipient 1") // Adds a primary recipient (required minimum)
            .addTo("recipient2@example.com", "Recipient 2") // Adds a second primary recipient
            .addCc("cc1@example.com", "CC Recipient 1") // Adds a CC recipient
            .addCc("cc2@example.com", "CC Recipient 2") // Adds a second CC recipient
            .addBcc("bcc1@example.com", "BCC Recipient 1") // Adds a BCC recipient
            .addBcc("bcc2@example.com", "BCC Recipient 2") // Adds a second BCC recipient
            .addAttachment(Attachment.builder().fromBase64("VGhpcyBpcyBhIHRlc3Qh", "test.txt").build()) // Adds an attachment from Base64-encoded text
            .addAttachment(Attachment.builder().fromFile("C:/temp/file.csv").build()) // Adds an attachment from a file
            .addAttachment(Attachment.builder().fromBytes(new byte[] {1, 2, 3}, "bytes.txt").build()) // Adds an attachment from a byte array
            .headerFrom("fancysender@example.com", "Header From") // Sets the header "From" field
            .addReplyTo("noreply@example.com", "No Reply") // Sets a Reply-To address
            .build(); // Constructs the Message, enforcing required fields (from, tos, subject, content)
    
    // Send the message asynchronously and wait for the result
    SendResult sendResult = client.send(message).join();
    
    // Output the HTTP status code from the API response
    System.out.println("HTTP Status: " + sendResult.getHttpResponse().statusCode());
    // Output the message ID from the API response
    System.out.println("Message ID: " + sendResult.getMessageId());
    // Output the reason (if any) from the API response
    System.out.println("Reason: " + sendResult.getReason());
    // Output the request ID from the API response
    System.out.println("Request ID: " + sendResult.getRequestId());
  }
}

Attachment MIME Type Deduction Behavior

• When creating attachments, the library automatically determines the MIME type based on the file extension.
• If the MIME type cannot be determined, an exception is raised.

// Create an attachment from disk; the MIME type will be "text/csv", and disposition will be "Disposition.Attachment"
Attachment.builder().fromFile("C:/temp/file.csv").build();

// This will throw an error, as the MIME type is unknown
Attachment.builder().fromFile("C:/temp/file.unknown").build();

// Create an attachment and specify the type information. The disposition will be "Disposition.Attachment", filename will be unknown.txt, and MIME type "text/plain"
Attachment.builder().fromFile("C:/temp/file.unknown").filename("unknown.txt").build();

// Create an attachment and specify the type information. The disposition will be "Disposition.Attachment", filename will be file.unknown, and MIME type "text/plain"
Attachment.builder().fromFile("C:/temp/file.unknown").mimeType("text/plain").build();

Inline Attachments and Content-IDs

When creating attachments, they are Disposition.Attachment by default. To use a Content-ID (e.g., <img src="cid:logo">) in HTML content, set the disposition to Disposition.Inline. The library supports both manual and auto-generated content IDs.

Using a Dynamically Generated Content-ID

// Create an inline attachment with an auto-generated content ID
Attachment logo = Attachment.builder().fromFile("C:/temp/logo.png").dispositionInline().build();
// Use the dynamic content ID in HTML content
Message message = Message.builder()
        .subject("Dynamic CID Test")
        .from("sender@example.com")
        .addTo("recipient@example.com")
        .addContent("<b>Test</b><br><img src=\"cid:" + logo.getContentId() + "\">", Content.ContentType.HTML)
        .addAttachment(logo)
        .build();

Setting a Custom Content-ID

Message message = Message.builder()
        .subject("Static CID Test")
        .from("sender@example.com")
        .addTo("recipient@example.com")
        .addContent("<b>Test</b><br><img src=\"cid:logo\">", Content.ContentType.HTML)
        .addAttachment(Attachment.builder().fromFile("C:/temp/logo.png").dispositionInline("logo").build())
        .build();

Concurrency Example

ExecutorService executorService = Executors.newFixedThreadPool(10);
Client client = new Client("<client_id>", "<client_secret>");
for (int i = 0; i < 10; i++) {
    executorService.submit(() -> {
        Message msg = Message.builder()
            .subject("Concurrent Test")
            .from("sender@example.com")
            .addTo("recipient@example.com")
            .addContent("Test message", Content.ContentType.TEXT)
            .build();
        SendResult result = client.send(msg).join();
        System.out.printf("Thread [%d] Status: %d\n", Thread.currentThread().getId(), result.getHttpResponse().statusCode());
    });
}
executorService.shutdown();
executorService.awaitTermination(60, TimeUnit.SECONDS);

Known Issues

There is a known issue where empty file content results in a 400 Bad Request error.

{
  "content": "",
  "disposition": "attachment",
  "filename": "empty.txt",
  "id": "1ed38149-70b2-4476-84a1-83e73913d43c",
  "type": "text/plain"
}

🔹 API Response:

Status Code: 400/BadRequest
Reason: attachments[0].content is required
Message ID:
Request ID: fe9a1acf60a20c9d90bed843f6530156
Raw JSON: {"request_id":"fe9a1acf60a20c9d90bed843f6530156","reason":"attachments[0].content is required"}

This issue has been reported to Proofpoint Product Management.

Limitations

• The Proofpoint API currently does not support empty file attachments.
• If an empty file is sent, you will receive a 400 Bad Request error.

Additional Resources

For more information, refer to the official Proofpoint Secure Email Relay API documentation:
API Documentation