diff --git a/cloud/start-server.sh b/cloud/start-server.sh
index dc2a203c..431a9c9c 100644
--- a/cloud/start-server.sh
+++ b/cloud/start-server.sh
@@ -17,5 +17,7 @@ docker run -d  --rm \
   -e POSTGRES_HOST=$POSTGRES_HOST \
   -e CORS_ALLOWED_ORIGINS=$CORS_ALLOWED_ORIGINS \
   -e SERVER_SERVLET_CONTEXT_PATH=$SERVER_SERVLET_CONTEXT_PATH \
+  -e MAILGUN_APIKEY=$MAILGUN_APIKEY \
+  -e SECURITY_KEY=$SECURITY_KEY \
   -e BUILD=ghcr.io/ricardo-campos-org/react-typescript-todolist/server:$PR \
   ghcr.io/ricardo-campos-org/react-typescript-todolist/server:$PR
diff --git a/server/pom.xml b/server/pom.xml
index 091fe8f8..638eb34b 100644
--- a/server/pom.xml
+++ b/server/pom.xml
@@ -100,10 +100,6 @@
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-security</artifactId>
     </dependency>
-    <dependency>
-      <groupId>org.springframework.boot</groupId>
-      <artifactId>spring-boot-starter-mail</artifactId>
-    </dependency>
 
     <!-- Database -->
     <dependency>
diff --git a/server/src/main/java/br/com/tasknoteapp/server/service/MailgunEmailService.java b/server/src/main/java/br/com/tasknoteapp/server/service/MailgunEmailService.java
index 4d44d230..ae691bb8 100644
--- a/server/src/main/java/br/com/tasknoteapp/server/service/MailgunEmailService.java
+++ b/server/src/main/java/br/com/tasknoteapp/server/service/MailgunEmailService.java
@@ -1,36 +1,29 @@
 package br.com.tasknoteapp.server.service;
 
 import br.com.tasknoteapp.server.entity.UserEntity;
-import br.com.tasknoteapp.server.exception.MailServiceException;
 import br.com.tasknoteapp.server.templates.MailgunTemplate;
 import br.com.tasknoteapp.server.templates.MailgunTemplateEmailChanged;
 import br.com.tasknoteapp.server.templates.MailgunTemplateResetPwd;
 import br.com.tasknoteapp.server.templates.MailgunTemplateResetPwdConfirm;
 import br.com.tasknoteapp.server.templates.MailgunTemplateSignUp;
-import java.nio.charset.StandardCharsets;
-import java.time.Duration;
-import java.util.Base64;
 import java.util.Objects;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.boot.restclient.RestTemplateBuilder;
-import org.springframework.http.HttpEntity;
-import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatusCode;
 import org.springframework.http.MediaType;
-import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Service;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.client.HttpClientErrorException;
-import org.springframework.web.client.RestTemplate;
+import org.springframework.web.client.RestClient;
 
 /** This service handles email messages for Mailgun. */
 @Service
 public class MailgunEmailService {
 
   private static final Logger logger = LoggerFactory.getLogger(MailgunEmailService.class.getName());
-  private final RestTemplate restTemplate;
+  private final RestClient restClient;
   private final String targetEnv;
   private final String domain;
   private String senderEmail;
@@ -42,23 +35,37 @@ public class MailgunEmailService {
    * @param domain The domain to send email from.
    * @param sender The from option.
    * @param targetEnv The environment.
-   * @param templateBuilder The template builder.
+   * @param restClientBuilder The rest client builder.
    */
   public MailgunEmailService(
       @Value("${mailgun.api-key}") String apiKey,
       @Value("${mailgun.domain}") String domain,
       @Value("${mailgun.sender-email}") String sender,
       @Value("${br.com.tasknote.server.target-env}") String targetEnv,
-      RestTemplateBuilder templateBuilder) {
+      RestClient.Builder restClientBuilder) {
     this.domain = domain;
     this.senderEmail = sender;
     this.targetEnv = targetEnv;
-    this.restTemplate =
-        templateBuilder
-            .connectTimeout(Duration.ofSeconds(5))
-            .readTimeout(Duration.ofSeconds(10))
-            .defaultHeader(HttpHeaders.AUTHORIZATION, basicAuth("api", apiKey))
-            .build();
+
+    if (apiKey != null && apiKey.length() > 6) {
+      logger.info(
+          "Mailgun API Key loaded: {}...{}",
+          apiKey.substring(0, 3),
+          apiKey.substring(apiKey.length() - 3));
+    } else {
+      logger.warn("Mailgun API Key is missing or too short!");
+    }
+
+    this.restClient = restClientBuilder
+        .baseUrl("https://api.mailgun.net/v3/" + domain)
+        .defaultStatusHandler(HttpStatusCode::isError, (request, response) -> {
+          logger.error(
+              "Mailgun API Error: {} {}",
+              response.getStatusCode(),
+              response.getStatusText());
+        })
+        .defaultHeaders(headers -> headers.setBasicAuth("api", apiKey))
+        .build();
   }
 
   /**
@@ -141,16 +148,11 @@ public void sendEmailChangedNotification(UserEntity user, String oldEmail) {
    *
    * @param to The target email address.
    * @param subject The message subject.
-   * @param textBody The message text body to be displayed.
-   * @param htmlBody The message html body to be rendered.
+   * @param template The mailgun template.
    */
   private void sendEmail(String to, String subject, MailgunTemplate template) {
-    String url = "https://api.mailgun.net/v3/" + domain + "/messages";
     String from = "TaskNote App <" + senderEmail + ">";
 
-    HttpHeaders headers = new HttpHeaders();
-    headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
-
     MultiValueMap<String, String> mailData = new LinkedMultiValueMap<>();
     mailData.add("from", from);
     mailData.add("to", to);
@@ -164,26 +166,22 @@ private void sendEmail(String to, String subject, MailgunTemplate template) {
       logger.info("JSON template variables: {}", template.getVariableValuesJson());
     }
 
-    HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(mailData, headers);
-
     try {
-      ResponseEntity<String> response = restTemplate.postForEntity(url, request, String.class);
-
-      if (!response.getStatusCode().is2xxSuccessful()) {
-        throw new MailServiceException("Failed to send email: " + response.getStatusCode());
-      }
+      restClient.post()
+          .uri("/messages")
+          .contentType(MediaType.APPLICATION_FORM_URLENCODED)
+          .body(mailData)
+          .retrieve()
+          .toBodilessEntity();
 
       logger.info("Email message send successfully.");
     } catch (HttpClientErrorException ex) {
-      logger.error("Unable to send email: {} - {}", ex.getMessage(), ex.getCause());
+      logger.error("Unable to send email: {} - {}", ex.getMessage(), ex.getStatusCode());
+    } catch (Exception ex) {
+      logger.error("Unexpected error sending email: {}", ex.getMessage());
     }
   }
 
-  private String basicAuth(String username, String password) {
-    String auth = username + ":" + password;
-    return "Basic " + Base64.getEncoder().encodeToString(auth.getBytes(StandardCharsets.UTF_8));
-  }
-
   private String getBaseUrl() {
     if ("development".equals(targetEnv) || Objects.isNull(targetEnv)) {
       return "http://localhost:5000";
diff --git a/server/src/test/java/br/com/tasknoteapp/server/service/MailgunEmailServiceTest.java b/server/src/test/java/br/com/tasknoteapp/server/service/MailgunEmailServiceTest.java
index 9afb562c..0c58e88c 100644
--- a/server/src/test/java/br/com/tasknoteapp/server/service/MailgunEmailServiceTest.java
+++ b/server/src/test/java/br/com/tasknoteapp/server/service/MailgunEmailServiceTest.java
@@ -2,7 +2,6 @@
 
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
-import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -13,34 +12,43 @@
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
-import org.springframework.boot.restclient.RestTemplateBuilder;
 import org.springframework.http.HttpStatusCode;
-import org.springframework.http.ResponseEntity;
 import org.springframework.web.client.HttpClientErrorException;
-import org.springframework.web.client.RestTemplate;
+import org.springframework.web.client.RestClient;
 
-/** Test class generated by Copilot. I had to tweak it, to make it work. */
+/** Test class for MailgunEmailService using RestClient. */
 @ExtendWith(MockitoExtension.class)
 class MailgunEmailServiceTest {
 
-  @Mock private RestTemplate restTemplate;
-  @Mock private RestTemplateBuilder restTemplateBuilder;
+  @Mock private RestClient restClient;
+  @Mock private RestClient.Builder restClientBuilder;
+  @Mock private RestClient.RequestBodyUriSpec requestBodyUriSpec;
+  @Mock private RestClient.RequestBodySpec requestBodySpec;
+  @Mock private RestClient.ResponseSpec responseSpec;
 
   private MailgunEmailService mailgunEmailService;
 
   @BeforeEach
   void setUp() {
-    when(restTemplateBuilder.connectTimeout(any())).thenReturn(restTemplateBuilder);
-    when(restTemplateBuilder.readTimeout(any())).thenReturn(restTemplateBuilder);
-    when(restTemplateBuilder.defaultHeader(any(), any())).thenReturn(restTemplateBuilder);
-    when(restTemplateBuilder.build()).thenReturn(restTemplate);
+    when(restClientBuilder.baseUrl(anyString())).thenReturn(restClientBuilder);
+    when(restClientBuilder.defaultStatusHandler(any(), any())).thenReturn(restClientBuilder);
+    when(restClientBuilder.defaultHeaders(any())).thenReturn(restClientBuilder);
+    when(restClientBuilder.build()).thenReturn(restClient);
 
     String apiKey = "abx123";
     String domain = "domain.com";
     String sender = "no-reply@domain.com";
     String target = "development";
     mailgunEmailService =
-        new MailgunEmailService(apiKey, domain, sender, target, restTemplateBuilder);
+        new MailgunEmailService(apiKey, domain, sender, target, restClientBuilder);
+  }
+
+  private void setupMockChain() {
+    when(restClient.post()).thenReturn(requestBodyUriSpec);
+    when(requestBodyUriSpec.uri(anyString())).thenReturn(requestBodySpec);
+    when(requestBodySpec.contentType(any())).thenReturn(requestBodySpec);
+    when(requestBodySpec.body(any())).thenReturn(requestBodySpec);
+    when(requestBodySpec.retrieve()).thenReturn(responseSpec);
   }
 
   @Test
@@ -49,12 +57,11 @@ void testSendResetPassword() {
     user.setEmail("test@example.com");
     user.setResetToken("reset-token");
 
-    when(restTemplate.postForEntity(anyString(), any(), eq(String.class)))
-        .thenReturn(ResponseEntity.ok("Success"));
+    setupMockChain();
 
     mailgunEmailService.sendResetPassword(user);
 
-    verify(restTemplate, times(1)).postForEntity(anyString(), any(), eq(String.class));
+    verify(restClient, times(1)).post();
   }
 
   @Test
@@ -62,12 +69,11 @@ void testSendPasswordResetConfirmation() {
     UserEntity user = new UserEntity();
     user.setEmail("test@example.com");
 
-    when(restTemplate.postForEntity(anyString(), any(), eq(String.class)))
-        .thenReturn(ResponseEntity.ok("Success"));
+    setupMockChain();
 
     mailgunEmailService.sendPasswordResetConfirmation(user);
 
-    verify(restTemplate, times(1)).postForEntity(anyString(), any(), eq(String.class));
+    verify(restClient, times(1)).post();
   }
 
   @Test
@@ -76,12 +82,11 @@ void testSendNewUser() {
     user.setEmail("test@example.com");
     user.setEmailUuid(java.util.UUID.randomUUID());
 
-    when(restTemplate.postForEntity(anyString(), any(), eq(String.class)))
-        .thenReturn(ResponseEntity.ok("Success"));
+    setupMockChain();
 
     mailgunEmailService.sendNewUser(user);
 
-    verify(restTemplate, times(1)).postForEntity(anyString(), any(), eq(String.class));
+    verify(restClient, times(1)).post();
   }
 
   @Test
@@ -90,12 +95,13 @@ void testSendEmailHandlesHttpClientErrorException() {
     user.setEmail("test@example.com");
     user.setResetToken("reset-token");
 
-    when(restTemplate.postForEntity(anyString(), any(), eq(String.class)))
+    setupMockChain();
+    when(responseSpec.toBodilessEntity())
         .thenThrow(new HttpClientErrorException(HttpStatusCode.valueOf(400)));
 
     mailgunEmailService.sendResetPassword(user);
 
-    verify(restTemplate, times(1)).postForEntity(anyString(), any(), eq(String.class));
+    verify(restClient, times(1)).post();
   }
 
   @Test
@@ -103,13 +109,12 @@ void testSendEmailChanged() {
     UserEntity user = new UserEntity();
     user.setEmail("test@example.com");
 
-    when(restTemplate.postForEntity(anyString(), any(), eq(String.class)))
-        .thenReturn(ResponseEntity.ok("Success"));
+    setupMockChain();
 
     String oldEmail = "old@example.com";
 
     mailgunEmailService.sendEmailChangedNotification(user, oldEmail);
 
-    verify(restTemplate, times(1)).postForEntity(anyString(), any(), eq(String.class));
+    verify(restClient, times(1)).post();
   }
 }