diff --git a/application/src/main/java/org/thingsboard/server/service/mail/TbMailSender.java b/application/src/main/java/org/thingsboard/server/service/mail/TbMailSender.java
index 6f98748dac..39c547c4f2 100644
--- a/application/src/main/java/org/thingsboard/server/service/mail/TbMailSender.java
+++ b/application/src/main/java/org/thingsboard/server/service/mail/TbMailSender.java
@@ -28,8 +28,6 @@ import org.springframework.lang.Nullable;
 import org.springframework.mail.javamail.JavaMailSenderImpl;
 import org.thingsboard.server.common.data.AdminSettings;
 import org.thingsboard.server.common.data.StringUtils;
-import org.thingsboard.server.common.data.exception.ThingsboardErrorCode;
-import org.thingsboard.server.common.data.exception.ThingsboardException;
 import org.thingsboard.server.common.data.id.TenantId;
 import org.thingsboard.server.common.data.mail.MailOauth2Provider;
 import org.thingsboard.server.dao.exception.IncorrectParameterException;
@@ -71,24 +69,28 @@ public class TbMailSender extends JavaMailSenderImpl {
     }
 
     @Override
-    public void doSend(MimeMessage[] mimeMessages, @Nullable Object[] originalMessages) {
+    protected void doSend(MimeMessage[] mimeMessages, @Nullable Object[] originalMessages) {
         updateOauth2PasswordIfExpired();
+        doSendSuper(mimeMessages, originalMessages);
+    }
+
+    protected void doSendSuper(MimeMessage[] mimeMessages, Object[] originalMessages) {
         super.doSend(mimeMessages, originalMessages);
     }
 
     @Override
     public void testConnection() throws MessagingException {
         updateOauth2PasswordIfExpired();
+        testConnectionSuper();
+    }
+
+    public void testConnectionSuper() throws MessagingException {
         super.testConnection();
     }
 
-    private void updateOauth2PasswordIfExpired() {
+    public void updateOauth2PasswordIfExpired() {
         if (oauth2Enabled && (System.currentTimeMillis() > tokenExpires)){
-            try {
-                refreshAccessToken();
-            } catch (ThingsboardException e) {
-                throw new RuntimeException(e);
-            }
+            refreshAccessToken();
             setPassword(accessToken);
         }
     }
@@ -138,7 +140,7 @@ public class TbMailSender extends JavaMailSenderImpl {
         return javaMailProperties;
     }
 
-    public void refreshAccessToken() throws ThingsboardException {
+    public void refreshAccessToken() {
         lock.lock();
         try {
             if (System.currentTimeMillis() > tokenExpires) {
@@ -164,8 +166,8 @@ public class TbMailSender extends JavaMailSenderImpl {
                 tokenExpires = System.currentTimeMillis() + (tokenResponse.getExpiresInSeconds().intValue() * 1000);
             }
         } catch (Exception e) {
-            log.warn("Unable to retrieve access token: {}", e.getMessage());
-            throw new ThingsboardException("Error while retrieving access token: " + e.getMessage(), ThingsboardErrorCode.GENERAL);
+            log.error("Unable to retrieve access token: {}", e.getMessage());
+            throw new RuntimeException("Error while retrieving access token: " + e.getMessage());
         } finally {
             lock.unlock();
         }
diff --git a/application/src/test/java/org/thingsboard/server/service/mail/TbMailSenderTest.java b/application/src/test/java/org/thingsboard/server/service/mail/TbMailSenderTest.java
new file mode 100644
index 0000000000..9beb8a4dd8
--- /dev/null
+++ b/application/src/test/java/org/thingsboard/server/service/mail/TbMailSenderTest.java
@@ -0,0 +1,98 @@
+package org.thingsboard.server.service.mail;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mockito;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.thingsboard.common.util.JacksonUtil;
+import javax.mail.MessagingException;
+import javax.mail.Session;
+import javax.mail.internet.MimeMessage;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Properties;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+
+@RunWith(MockitoJUnitRunner.class)
+public class TbMailSenderTest {
+
+    @Test
+    public void testDoSendSendMail() {
+        ObjectNode jsonConfig = getBasicMailConfig();
+        TbMailSender tbMailSender = spy(new TbMailSender(mock(TbMailContextComponent.class), jsonConfig));
+
+        MimeMessage mimeMsg = new MimeMessage(Session.getInstance(new Properties()));
+        List<MimeMessage> mimeMessages = new ArrayList<>(1);
+        mimeMessages.add(mimeMsg);
+
+        Mockito.doNothing().when(tbMailSender).updateOauth2PasswordIfExpired();
+        Mockito.doNothing().when(tbMailSender).doSendSuper(any(), any());
+
+        tbMailSender.doSend(mimeMessages.toArray(new MimeMessage[0]), null);
+
+        Mockito.verify(tbMailSender, times(1)).updateOauth2PasswordIfExpired();
+    }
+
+    @Test
+    public void testTestConnection() throws MessagingException {
+        ObjectNode jsonConfig = getBasicMailConfig();
+        TbMailSender tbMailSender = spy(new TbMailSender(mock(TbMailContextComponent.class), jsonConfig));
+
+        Mockito.doNothing().when(tbMailSender).updateOauth2PasswordIfExpired();
+        Mockito.doNothing().when(tbMailSender).testConnectionSuper();
+
+        tbMailSender.testConnection();
+
+        Mockito.verify(tbMailSender, times(1)).updateOauth2PasswordIfExpired();
+    }
+
+    @Test
+    public void testUpdateOauth2PasswordIfExpiredIfOauth2Enabled() {
+        ObjectNode jsonConfig = getOauth2Config();
+        TbMailSender tbMailSender = spy(new TbMailSender(mock(TbMailContextComponent.class), jsonConfig));
+
+        Mockito.doNothing().when(tbMailSender).refreshAccessToken();
+
+        tbMailSender.updateOauth2PasswordIfExpired();
+
+        Mockito.verify(tbMailSender, times(1)).refreshAccessToken();
+        Mockito.verify(tbMailSender, times(1)).setPassword(any());
+    }
+
+    @Test
+    public void testUpdateOauth2PasswordIfExpiredIfOauth2Disabled() {
+        ObjectNode jsonConfig = getBasicMailConfig();
+        TbMailSender tbMailSender = spy(new TbMailSender(mock(TbMailContextComponent.class), jsonConfig));
+
+        tbMailSender.updateOauth2PasswordIfExpired();
+
+        Mockito.verify(tbMailSender, Mockito.never()).refreshAccessToken();
+        Mockito.verify(tbMailSender, Mockito.never()).setPassword(any());
+    }
+
+    private static ObjectNode getOauth2Config() {
+        ObjectNode jsonConfig = JacksonUtil.newObjectNode();
+        jsonConfig.put("smtpProtocol", "smtps");
+        jsonConfig.put("timeout", "1000");
+        jsonConfig.put("enableOauth2", true);
+        jsonConfig.put("smtpHost", "smtp.gmail.com");
+        jsonConfig.put("smtpPort", "465");
+        jsonConfig.put("username", "testUser");
+        return jsonConfig;
+    }
+
+    private static ObjectNode getBasicMailConfig() {
+        ObjectNode jsonConfig = JacksonUtil.newObjectNode();
+        jsonConfig.put("smtpProtocol", "smtps");
+        jsonConfig.put("timeout", "1000");
+        jsonConfig.put("smtpHost", "smtp.gmail.com");
+        jsonConfig.put("smtpPort", "465");
+        jsonConfig.put("username", "testUser");
+        return jsonConfig;
+    }
+}