diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index 2ecc26f..a31dd6d 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -17,7 +17,7 @@ spotless {
 }
 
 group = "com.nuntly"
-version = "1.0.0-alpha.17"
+version = "1.0.0-alpha.18"
 
 mavenPublishing {
     publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL, automaticRelease = true)
diff --git a/sdk/build.gradle.kts b/sdk/build.gradle.kts
index 91eb837..16088f7 100644
--- a/sdk/build.gradle.kts
+++ b/sdk/build.gradle.kts
@@ -17,7 +17,7 @@ spotless {
 }
 
 group = "com.nuntly"
-version = "1.0.0-alpha.17"
+version = "1.0.0-alpha.18"
 
 mavenPublishing {
     publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL, automaticRelease = true)
diff --git a/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmail.java b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmail.java
new file mode 100644
index 0000000..a867ae3
--- /dev/null
+++ b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmail.java
@@ -0,0 +1,32 @@
+package com.nuntly.sdk.models;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+public record CreateBulkEmail(
+    /** The e-mail address of the sender */
+    Optional<String> from,
+    /** The primary recipient(s) of the email */
+    List<String> to,
+    /** The carbon copy recipient(s) of the email */
+    List<String> cc,
+    /** The blind carbon copy recipient(s) of the email */
+    List<String> bcc,
+    /**
+     * The email address where replies should be sent. If a recipient replies, the response will go
+     * to this address instead of the sender's email address
+     */
+    List<String> replyTo,
+    /** The subject of the e-mail */
+    Optional<String> subject,
+    /** The plaintext version of the email */
+    Optional<String> text,
+    /** The HTML version of the email */
+    Optional<String> html,
+    /** The headers to add to the email */
+    Map<String, String> headers,
+    /** The tags to add to the email */
+    List<Tag> tags,
+    /** The variables for the template */
+    Map<String, Object> variables) {}
diff --git a/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmailsRequest.java b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmailsRequest.java
index 9cc1865..a1f843f 100644
--- a/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmailsRequest.java
+++ b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkEmailsRequest.java
@@ -1,7 +1,7 @@
 package com.nuntly.sdk.models;
 
 import java.util.List;
-import java.util.Map;
+import java.util.Optional;
 
 /**
  *
@@ -13,33 +13,33 @@
  * }</pre>
  */
 public record CreateBulkEmailsRequest(
-    /** Used as a fallback field email value if no value is present in emails */
-    Map<String, Object> fallback,
-    /** The bulk emails to send */
-    List<Map<String, Object>> emails) {
+    /** Used as a fallback field email value if no value is present in emails. */
+    Optional<CreateBulkFallback> fallback,
+    /** The bulk emails to send. */
+    List<CreateBulkEmail> emails) {
 
   public static Builder builder() {
     return new Builder();
   }
 
   public static final class Builder {
-    private Map<String, Object> fallback;
-    private List<Map<String, Object>> emails;
+    private CreateBulkFallback fallback;
+    private List<CreateBulkEmail> emails;
 
-    /** Used as a fallback field email value if no value is present in emails */
-    public Builder fallback(Map<String, Object> fallback) {
+    /** Used as a fallback field email value if no value is present in emails. */
+    public Builder fallback(CreateBulkFallback fallback) {
       this.fallback = fallback;
       return this;
     }
 
-    /** The bulk emails to send */
-    public Builder emails(List<Map<String, Object>> emails) {
+    /** The bulk emails to send. */
+    public Builder emails(List<CreateBulkEmail> emails) {
       this.emails = emails;
       return this;
     }
 
     public CreateBulkEmailsRequest build() {
-      return new CreateBulkEmailsRequest(fallback, emails);
+      return new CreateBulkEmailsRequest(Optional.ofNullable(fallback), emails);
     }
   }
 }
diff --git a/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkFallback.java b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkFallback.java
new file mode 100644
index 0000000..4192c30
--- /dev/null
+++ b/sdk/src/main/java/com/nuntly/sdk/models/CreateBulkFallback.java
@@ -0,0 +1,32 @@
+package com.nuntly.sdk.models;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+public record CreateBulkFallback(
+    /** The e-mail address of the sender */
+    Optional<String> from,
+    /** The primary recipient(s) of the email */
+    List<String> to,
+    /** The carbon copy recipient(s) of the email */
+    List<String> cc,
+    /** The blind carbon copy recipient(s) of the email */
+    List<String> bcc,
+    /**
+     * The email address where replies should be sent. If a recipient replies, the response will go
+     * to this address instead of the sender's email address
+     */
+    List<String> replyTo,
+    /** The subject of the e-mail */
+    Optional<String> subject,
+    /** The plaintext version of the email */
+    Optional<String> text,
+    /** The HTML version of the email */
+    Optional<String> html,
+    /** The headers to add to the email */
+    Map<String, String> headers,
+    /** The tags to add to the email */
+    List<Tag> tags,
+    /** The variables for the template */
+    Map<String, Object> variables) {}
diff --git a/spring/build.gradle.kts b/spring/build.gradle.kts
index adc1fea..ae14f0a 100644
--- a/spring/build.gradle.kts
+++ b/spring/build.gradle.kts
@@ -17,7 +17,7 @@ spotless {
 }
 
 group = "com.nuntly"
-version = "1.0.0-alpha.17"
+version = "1.0.0-alpha.18"
 
 mavenPublishing {
     publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL, automaticRelease = true)