#3542 Optimized mail configuration (#3544)

* #3542 Optimized mail configuration

* #3542 Optimized mail configuration
Co-authored-by: Nwangjianda <Felix@thinkingdata.com>

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/utils/MailUtils.java

@@ -59,7 +59,7 @@ public class MailUtils {
 
     public static final String STARTTLS_ENABLE = PropertyUtils.getString(Constants.MAIL_SMTP_STARTTLS_ENABLE);
 
-    public static final String SSL_ENABLE = PropertyUtils.getString(Constants.MAIL_SMTP_SSL_ENABLE);
+    public static final Boolean SSL_ENABLE = PropertyUtils.getBoolean(Constants.MAIL_SMTP_SSL_ENABLE);
 
     public static final String SSL_TRUST = PropertyUtils.getString(Constants.MAIL_SMTP_SSL_TRUST);
 
@@ -213,6 +213,7 @@ public class MailUtils {
 
     /**
      * get session
+     *
      * @return the new Session
      */
     private static Session getSession() {
@@ -222,8 +223,10 @@ public class MailUtils {
         props.setProperty(Constants.MAIL_SMTP_AUTH, Constants.STRING_TRUE);
         props.setProperty(Constants.MAIL_TRANSPORT_PROTOCOL, MAIL_PROTOCOL);
         props.setProperty(Constants.MAIL_SMTP_STARTTLS_ENABLE, STARTTLS_ENABLE);
-        props.setProperty(Constants.MAIL_SMTP_SSL_ENABLE, SSL_ENABLE);
-        props.setProperty(Constants.MAIL_SMTP_SSL_TRUST, SSL_TRUST);
+        if (SSL_ENABLE) {
+            props.setProperty(Constants.MAIL_SMTP_SSL_ENABLE, "true");
+            props.setProperty(Constants.MAIL_SMTP_SSL_TRUST, SSL_TRUST);
+        }
 
         Authenticator auth = new Authenticator() {
             @Override
@@ -345,5 +348,5 @@ public class MailUtils {
         retMap.put(Constants.MESSAGE, "Send email to {" + String.join(",", receivers) + "} failed，" + e.toString());
     }
 
-    
+
 }