diff --git a/core/src/test/java/cn/edu/tsinghua/iginx/notice/EmailNotifierTest.java b/core/src/test/java/cn/edu/tsinghua/iginx/notice/EmailNotifierTest.java
index 8cafe5e9e3..1269edabba 100644
--- a/core/src/test/java/cn/edu/tsinghua/iginx/notice/EmailNotifierTest.java
+++ b/core/src/test/java/cn/edu/tsinghua/iginx/notice/EmailNotifierTest.java
@@ -32,6 +32,7 @@
 import javax.mail.MessagingException;
 import javax.mail.internet.MimeMessage;
 import org.apache.commons.mail.EmailException;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -62,6 +63,9 @@ public void before() {
   @Test
   public void testSendEmail() throws MessagingException, EmailException {
     emailNotifier.sendEmail("subject", "body");
+
+    Assert.assertTrue(greenMail.waitForIncomingEmail(10 * 1000, 1));
+
     assertEquals(1, greenMail.getReceivedMessages().length);
     MimeMessage mimeMessage = greenMail.getReceivedMessages()[0];
 
@@ -81,6 +85,9 @@ public void testNotifyJobState() throws MessagingException, EmailException {
     job.setState(JobState.JOB_FINISHED);
     job.setEndTime(1716384072743L);
     emailNotifier.send(job);
+
+    Assert.assertTrue(greenMail.waitForIncomingEmail(10 * 1000, 1));
+
     assertEquals(1, greenMail.getReceivedMessages().length);
     MimeMessage mimeMessage = greenMail.getReceivedMessages()[0];
 
@@ -102,6 +109,9 @@ public void testNotifyJobStateException() throws MessagingException, EmailExcept
     job.setState(JobState.JOB_FINISHED);
     job.setEndTime(1716384072743L);
     emailNotifier.send(job);
+
+    Assert.assertTrue(greenMail.waitForIncomingEmail(10 * 1000, 1));
+
     assertEquals(1, greenMail.getReceivedMessages().length);
     MimeMessage mimeMessage = greenMail.getReceivedMessages()[0];
 
diff --git a/test/src/test/java/cn/edu/tsinghua/iginx/integration/func/udf/TransformIT.java b/test/src/test/java/cn/edu/tsinghua/iginx/integration/func/udf/TransformIT.java
index c6e2f5a03f..9e3c46945c 100644
--- a/test/src/test/java/cn/edu/tsinghua/iginx/integration/func/udf/TransformIT.java
+++ b/test/src/test/java/cn/edu/tsinghua/iginx/integration/func/udf/TransformIT.java
@@ -999,6 +999,8 @@ public void commitSingleSqlStatementByYamlWithEmailTest() throws MessagingExcept
       long jobId = result.getJobId();
       verifyJobState(jobId);
 
+      Assert.assertTrue(greenMail.waitForIncomingEmail(10 * 1000, 2));
+
       assertEquals(2, greenMail.getReceivedMessages().length);
       assertEquals("Job " + jobId + " is created", greenMail.getReceivedMessages()[0].getSubject());
       assertEquals(