nylas · AaronDDM · Aug 28, 2025 · Aug 28, 2025
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Added
+* `is_plaintext` support in `SendMessageRequest` and `CreateDraftRequest` to control plain text vs HTML message formatting
+
 ### Changed
 * `SendMessageRequest.sendAt` field changed from `Int?` to `Long?` to support Unix timestamps beyond 2038. Maintains backward compatibility through method overloading - existing `Int` parameters are automatically converted to `Long`. **Note:** Kotlin users passing integer literals may need to specify type explicitly (e.g., `1620000000L` or `1620000000 as Int`).
 

diff --git a/examples/src/main/java/com/nylas/examples/MessagesExample.java b/examples/src/main/java/com/nylas/examples/MessagesExample.java
@@ -1,6 +1,7 @@
 package com.nylas.examples;
 
 import com.nylas.NylasClient;
+import com.nylas.models.EmailName;
 import com.nylas.models.FindMessageQueryParams;
 import com.nylas.models.ListMessagesQueryParams;
 import com.nylas.models.ListResponse;
@@ -9,6 +10,7 @@
 import com.nylas.models.NylasApiError;
 import com.nylas.models.NylasSdkTimeoutError;
 import com.nylas.models.Response;
+import com.nylas.models.SendMessageRequest;
 import com.nylas.models.TrackingOptions;
 import okhttp3.OkHttpClient;
 
@@ -134,6 +136,9 @@ private static void runMessagesExample(NylasClient nylas, Map<String, String> co
 
         // 5. Find a specific message with different field options
         demonstrateMessageFinding(nylas, grantId);
+
+        // 6. Demonstrate is_plaintext feature for sending messages
+        demonstratePlaintextFeature(nylas, grantId, config);
     }
 
     private static void demonstrateStandardMessageListing(NylasClient nylas, String grantId) throws NylasApiError, NylasSdkTimeoutError {
@@ -301,4 +306,60 @@ private static void printMessageDetails(Message message, String requestType) {
             System.out.println("     Raw MIME length: " + message.getRawMime().length() + " characters");
         }
     }
+
+    private static void demonstratePlaintextFeature(NylasClient nylas, String grantId, Map<String, String> config) throws NylasApiError, NylasSdkTimeoutError {
+        System.out.println("📝 6. Demonstrating is_plaintext feature for sending messages (NEW FEATURE):");
+
+        String recipientEmail = config.get("NYLAS_RECIPIENT_EMAIL");
+        if (recipientEmail == null) {
+            System.out.println("   ⚠️  Skipping send examples - NYLAS_RECIPIENT_EMAIL not configured");
+            System.out.println("   To enable this demo, set NYLAS_RECIPIENT_EMAIL in your .env file");
+            return;
+        }
+
+        System.out.println("   Sending test messages to: " + recipientEmail);
+
+        // 1. Send HTML message (default behavior)
+        System.out.println("\n   📧 Sending HTML message (is_plaintext = false or not specified):");
+
+        SendMessageRequest htmlRequest = new SendMessageRequest.Builder(
+            Arrays.asList(new EmailName(recipientEmail, "Test Recipient"))
+        )
+            .subject("HTML Message Test - Nylas SDK")
+            .body("<html><body><h1>Hello from Nylas!</h1><p>This is an <b>HTML</b> message with <i>formatting</i>.</p></body></html>")
+            .isPlaintext(false) // Explicitly set to false (this is also the default)
+            .build();
+
+        try {
+            Response<Message> htmlResponse = nylas.messages().send(grantId, htmlRequest);
+            System.out.println("     ✅ HTML message sent successfully");
+            System.out.println("     Message ID: " + htmlResponse.getData().getId());
+        } catch (Exception e) {
+            System.out.println("     ❌ Failed to send HTML message: " + e.getMessage());
+        }
+
+        // 2. Send plain text message using is_plaintext feature
+        System.out.println("\n   📄 Sending plain text message (is_plaintext = true):");
+
+        SendMessageRequest plaintextRequest = new SendMessageRequest.Builder(
+            Arrays.asList(new EmailName(recipientEmail, "Test Recipient"))
+        )
+            .subject("Plain Text Message Test - Nylas SDK")
+            .body("Hello from Nylas!\n\nThis is a PLAIN TEXT message.\nNo HTML formatting will be applied.\n\nBest regards,\nNylas SDK")
+            .isPlaintext(true) // NEW FEATURE: Force plain text mode
+            .build();
+
+        try {
+            Response<Message> plaintextResponse = nylas.messages().send(grantId, plaintextRequest);
+            System.out.println("     ✅ Plain text message sent successfully");
+            System.out.println("     Message ID: " + plaintextResponse.getData().getId());
+        } catch (Exception e) {
+            System.out.println("     ❌ Failed to send plain text message: " + e.getMessage());
+        }
+
+        System.out.println("\n   💡 Key differences:");
+        System.out.println("     - HTML message (is_plaintext=false): Message body is sent as HTML with MIME formatting");
+        System.out.println("     - Plain text message (is_plaintext=true): Message body is sent as plain text, no HTML in MIME data");
+        System.out.println("     - Default behavior: is_plaintext=false (HTML formatting)");
+    }
 } 
diff --git a/examples/src/main/kotlin/com/nylas/examples/KotlinMessagesExample.kt b/examples/src/main/kotlin/com/nylas/examples/KotlinMessagesExample.kt
@@ -117,6 +117,9 @@ private fun runMessagesExample(nylas: NylasClient, config: Map<String, String>)
 
     // 5. Find a specific message with different field options
     demonstrateMessageFinding(nylas, grantId)
+
+    // 6. Demonstrate is_plaintext feature for sending messages
+    demonstratePlaintextFeature(nylas, grantId, config)
 }
 
 private fun demonstrateStandardMessageListing(nylas: NylasClient, grantId: String) {
@@ -277,4 +280,60 @@ private fun printMessageDetails(message: Message, requestType: String) {
     message.rawMime?.let { rawMime ->
         println("     Raw MIME length: ${rawMime.length} characters")
     }
+}
+
+private fun demonstratePlaintextFeature(nylas: NylasClient, grantId: String, config: Map<String, String>) {
+    println("📝 6. Demonstrating is_plaintext feature for sending messages (NEW FEATURE):")
+
+    val recipientEmail = config["NYLAS_RECIPIENT_EMAIL"]
+    if (recipientEmail == null) {
+        println("   ⚠️  Skipping send examples - NYLAS_RECIPIENT_EMAIL not configured")
+        println("   To enable this demo, set NYLAS_RECIPIENT_EMAIL in your .env file")
+        return
+    }
+
+    println("   Sending test messages to: $recipientEmail")
+
+    // 1. Send HTML message (default behavior)
+    println("\n   📧 Sending HTML message (is_plaintext = false or not specified):")
+
+    val htmlRequest = SendMessageRequest.Builder(
+        listOf(EmailName(recipientEmail, "Test Recipient"))
+    )
+        .subject("HTML Message Test - Nylas SDK")
+        .body("<html><body><h1>Hello from Nylas!</h1><p>This is an <b>HTML</b> message with <i>formatting</i>.</p></body></html>")
+        .isPlaintext(false) // Explicitly set to false (this is also the default)
+        .build()
+
+    try {
+        val htmlResponse = nylas.messages().send(grantId, htmlRequest)
+        println("     ✅ HTML message sent successfully")
+        println("     Message ID: ${htmlResponse.data.id}")
+    } catch (e: Exception) {
+        println("     ❌ Failed to send HTML message: ${e.message}")
+    }
+
+    // 2. Send plain text message using is_plaintext feature
+    println("\n   📄 Sending plain text message (is_plaintext = true):")
+
+    val plaintextRequest = SendMessageRequest.Builder(
+        listOf(EmailName(recipientEmail, "Test Recipient"))
+    )
+        .subject("Plain Text Message Test - Nylas SDK")
+        .body("Hello from Nylas!\n\nThis is a PLAIN TEXT message.\nNo HTML formatting will be applied.\n\nBest regards,\nNylas SDK")
+        .isPlaintext(true) // NEW FEATURE: Force plain text mode
+        .build()
+
+    try {
+        val plaintextResponse = nylas.messages().send(grantId, plaintextRequest)
+        println("     ✅ Plain text message sent successfully")
+        println("     Message ID: ${plaintextResponse.data.id}")
+    } catch (e: Exception) {
+        println("     ❌ Failed to send plain text message: ${e.message}")
+    }
+
+    println("\n   💡 Key differences:")
+    println("     - HTML message (is_plaintext=false): Message body is sent as HTML with MIME formatting")
+    println("     - Plain text message (is_plaintext=true): Message body is sent as plain text, no HTML in MIME data")
+    println("     - Default behavior: is_plaintext=false (HTML formatting)")
 } 
diff --git a/src/main/kotlin/com/nylas/models/CreateDraftRequest.kt b/src/main/kotlin/com/nylas/models/CreateDraftRequest.kt
@@ -72,6 +72,12 @@ data class CreateDraftRequest(
    */
   @Json(name = "custom_headers")
   val customHeaders: List<CustomHeader>? = null,
+  /**
+   * When true, the message body is sent as plain text and the MIME data doesn't include the HTML version of the message.
+   * When false, the message body is sent as HTML.
+   */
+  @Json(name = "is_plaintext")
+  val isPlaintext: Boolean? = null,
 ) : IMessageAttachmentRequest {
   /**
    * Builder for [CreateDraftRequest].
@@ -90,6 +96,7 @@ data class CreateDraftRequest(
     private var replyToMessageId: String? = null
     private var trackingOptions: TrackingOptions? = null
     private var customHeaders: List<CustomHeader>? = null
+    private var isPlaintext: Boolean? = null
 
     /**
      * Sets the from address.
@@ -184,8 +191,17 @@ data class CreateDraftRequest(
     fun customHeaders(customHeaders: List<CustomHeader>?) = apply { this.customHeaders = customHeaders }
 
     /**
-     * Builds a [SendMessageRequest] instance.
-     * @return The [SendMessageRequest] instance.
+     * Sets whether the message body is sent as plain text.
+     * When true, the message body is sent as plain text and the MIME data doesn't include the HTML version of the message.
+     * When false, the message body is sent as HTML.
+     * @param isPlaintext Whether the message body is sent as plain text.
+     * @return The builder.
+     */
+    fun isPlaintext(isPlaintext: Boolean?) = apply { this.isPlaintext = isPlaintext }
+
+    /**
+     * Builds a [CreateDraftRequest] instance.
+     * @return The [CreateDraftRequest] instance.
      */
     fun build() =
       CreateDraftRequest(
@@ -202,6 +218,7 @@ data class CreateDraftRequest(
         replyToMessageId,
         trackingOptions,
         customHeaders,
+        isPlaintext,
       )
   }
 }
diff --git a/src/main/kotlin/com/nylas/models/SendMessageRequest.kt b/src/main/kotlin/com/nylas/models/SendMessageRequest.kt
@@ -78,6 +78,12 @@ data class SendMessageRequest(
    */
   @Json(name = "custom_headers")
   val customHeaders: List<CustomHeader>? = null,
+  /**
+   * When true, the message body is sent as plain text and the MIME data doesn't include the HTML version of the message.
+   * When false, the message body is sent as HTML.
+   */
+  @Json(name = "is_plaintext")
+  val isPlaintext: Boolean? = null,
 ) : IMessageAttachmentRequest {
   /**
    * Builder for [SendMessageRequest].
@@ -99,6 +105,7 @@ data class SendMessageRequest(
     private var trackingOptions: TrackingOptions? = null
     private var useDraft: Boolean? = null
     private var customHeaders: List<CustomHeader>? = null
+    private var isPlaintext: Boolean? = null
 
     /**
      * Sets the bcc recipients.
@@ -200,6 +207,15 @@ data class SendMessageRequest(
      */
     fun customHeaders(customHeaders: List<CustomHeader>?) = apply { this.customHeaders = customHeaders }
 
+    /**
+     * Sets whether the message body is sent as plain text.
+     * When true, the message body is sent as plain text and the MIME data doesn't include the HTML version of the message.
+     * When false, the message body is sent as HTML.
+     * @param isPlaintext Whether the message body is sent as plain text.
+     * @return The builder.
+     */
+    fun isPlaintext(isPlaintext: Boolean?) = apply { this.isPlaintext = isPlaintext }
+
     /**
      * Builds a [SendMessageRequest] instance.
      * @return The [SendMessageRequest] instance.
@@ -220,6 +236,7 @@ data class SendMessageRequest(
         trackingOptions,
         useDraft,
         customHeaders,
+        isPlaintext,
       )
   }
 }
diff --git a/src/test/kotlin/com/nylas/resources/DraftsTests.kt b/src/test/kotlin/com/nylas/resources/DraftsTests.kt
@@ -19,8 +19,10 @@ import java.io.ByteArrayInputStream
 import java.lang.reflect.Type
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertFalse
 import kotlin.test.assertIs
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class DraftsTests {
   private val mockHttpClient: OkHttpClient = Mockito.mock(OkHttpClient::class.java)
@@ -254,6 +256,67 @@ class DraftsTests {
       assertNull(queryParamCaptor.firstValue)
     }
 
+    @Test
+    fun `creating a draft with is_plaintext true serializes correctly`() {
+      val adapter = JsonHelper.moshi().adapter(CreateDraftRequest::class.java)
+      val createDraftRequest =
+        CreateDraftRequest(
+          body = "Hello, I just created a draft using Nylas!",
+          subject = "Hello from Nylas!",
+          isPlaintext = true,
+        )
+
+      val serializedRequest = adapter.toJson(createDraftRequest)
+      assertTrue(serializedRequest.contains("\"is_plaintext\":true"))
+
+      drafts.create(grantId, createDraftRequest)
+
+      val pathCaptor = argumentCaptor<String>()
+      val typeCaptor = argumentCaptor<Type>()
+      val requestBodyCaptor = argumentCaptor<String>()
+      val queryParamCaptor = argumentCaptor<IQueryParams>()
+      val overrideParamCaptor = argumentCaptor<RequestOverrides>()
+      verify(mockNylasClient).executePost<Response<Draft>>(
+        pathCaptor.capture(),
+        typeCaptor.capture(),
+        requestBodyCaptor.capture(),
+        queryParamCaptor.capture(),
+        overrideParamCaptor.capture(),
+      )
+
+      assertEquals("v3/grants/$grantId/drafts", pathCaptor.firstValue)
+      assertEquals(Types.newParameterizedType(Response::class.java, Draft::class.java), typeCaptor.firstValue)
+      assertEquals(adapter.toJson(createDraftRequest), requestBodyCaptor.firstValue)
+      assertNull(queryParamCaptor.firstValue)
+    }
+
+    @Test
+    fun `creating a draft with is_plaintext false or not specified defaults correctly`() {
+      val adapter = JsonHelper.moshi().adapter(CreateDraftRequest::class.java)
+
+      // Test with explicit false
+      val createDraftRequestFalse =
+        CreateDraftRequest(
+          body = "Hello, I just created a draft using Nylas!",
+          subject = "Hello from Nylas!",
+          isPlaintext = false,
+        )
+
+      val serializedRequestFalse = adapter.toJson(createDraftRequestFalse)
+      assertTrue(serializedRequestFalse.contains("\"is_plaintext\":false"))
+
+      // Test with not specified (should default to false)
+      val createDraftRequestDefault =
+        CreateDraftRequest(
+          body = "Hello, I just created a draft using Nylas!",
+          subject = "Hello from Nylas!",
+        )
+
+      val serializedRequestDefault = adapter.toJson(createDraftRequestDefault)
+      // When null/not specified, the field should not be included in JSON or be false
+      assertFalse(serializedRequestDefault.contains("\"is_plaintext\":true"))
+    }
+
     @Test
     fun `creating a draft with small attachment calls requests with the correct params`() {
       val adapter = JsonHelper.moshi().adapter(CreateDraftRequest::class.java)