Add MailClient that uses Java Mail API to send emails. Use it instead of Mailgun client.

Mage.Server/config/config.xml

@@ -41,6 +41,11 @@
             googleAccount=""
             mailgunApiKey=""
             mailgunDomain=""
+            mailSmtpHost=""
+            mailSmtpPort=""
+            mailUser=""
+            mailPassword=""
+            mailFromAddress=""
     />
     <playerTypes>
         <playerType name="Human" jar="mage-player-human.jar" className="mage.player.human.HumanPlayer"/>

Mage.Server/src/main/java/mage/server/MageServerImpl.java

@@ -140,7 +140,7 @@ public class MageServerImpl implements MageServer {
         }
         String authToken = generateAuthToken();
         activeAuthTokens.put(email, authToken);
-        if (!MailgunClient.sendMessage(email, "XMage Password Reset Auth Token",
+        if (!MailClient.sendMessage(email, "XMage Password Reset Auth Token",
                 "Use this auth token to reset your password: " + authToken + "\n" +
                 "It's valid until the next server restart.")) {
             sendErrorMessageToClient(sessionId, "There was an error inside the server while emailing an auth token");

Mage.Server/src/main/java/mage/server/MailClient.java

@@ -0,0 +1,53 @@
+package mage.server;
+
+import java.util.Properties;
+import javax.mail.Message;
+import javax.mail.MessagingException;
+import javax.mail.Session;
+import javax.mail.Transport;
+import javax.mail.internet.InternetAddress;
+import javax.mail.internet.MimeMessage;
+import mage.server.util.ConfigSettings;
+import org.apache.log4j.Logger;
+
+public class MailClient {
+
+    private static final Logger logger = Logger.getLogger(Main.class);
+
+    public static boolean sendMessage(String email, String subject, String text) {
+        if (email.length() == 0) {
+            logger.info("Email is not sent because the address is empty");
+            return false;
+        }
+        ConfigSettings config = ConfigSettings.getInstance();
+
+        Properties properties = System.getProperties();
+        properties.setProperty("mail.smtps.host", config.getMailSmtpHost());
+        properties.setProperty("mail.smtps.port", config.getMailSmtpPort());
+        properties.setProperty("mail.smtps.auth", "true");
+        properties.setProperty("mail.user", config.getMailUser());
+        properties.setProperty("mail.password", config.getMailPassword());
+
+        Session session = Session.getDefaultInstance(properties);
+
+        try{
+            MimeMessage message = new MimeMessage(session);
+            message.setFrom(new InternetAddress(config.getMailFromAddress()));
+            message.addRecipient(Message.RecipientType.TO, new InternetAddress(email));
+            message.setSubject(subject);
+            message.setText(text);
+
+            Transport trnsport;
+            trnsport = session.getTransport("smtps");
+            trnsport.connect(null, properties.getProperty("mail.password"));
+            message.saveChanges();
+            trnsport.sendMessage(message, message.getAllRecipients());
+            trnsport.close();
+
+            return true;
+        }catch (MessagingException ex) {
+            logger.error("Error sending message to " + email, ex);
+        }
+        return false;
+    }
+}

Mage.Server/src/main/java/mage/server/Session.java

@@ -99,7 +99,7 @@ public class Session {
                 return returnMessage;
             }
             AuthorizedUserRepository.instance.add(userName, password, email);
-            if (MailgunClient.sendMessage(email, "XMage Registration Completed",
+            if (MailClient.sendMessage(email, "XMage Registration Completed",
                     "You are successfully registered as " + userName + ".")) {
                 logger.info("Sent a registration confirmation email to " + email + " for " + userName);
             } else {

Mage.Server/src/main/java/mage/server/util/ConfigSettings.java

@@ -147,6 +147,26 @@ public class ConfigSettings {
         return config.getServer().getMailgunDomain();
     }
 
+    public String getMailSmtpHost() {
+        return config.getServer().getMailSmtpHost();
+    }
+
+    public String getMailSmtpPort() {
+        return config.getServer().getMailSmtpPort();
+    }
+
+    public String getMailUser() {
+        return config.getServer().getMailUser();
+    }
+
+    public String getMailPassword() {
+        return config.getServer().getMailPassword();
+    }
+
+    public String getMailFromAddress() {
+        return config.getServer().getMailFromAddress();
+    }
+
     public List<Plugin> getPlayerTypes() {
         return config.getPlayerTypes().getPlayerType();
     }

Mage.Server/src/main/xml-resources/jaxb/Config/Config.xsd

@@ -38,6 +38,11 @@
 			<xs:attribute name="googleAccount" type="xs:string" use="optional"/>
 			<xs:attribute name="mailgunApiKey" type="xs:string" use="optional"/>
 			<xs:attribute name="mailgunDomain" type="xs:string" use="optional"/>
+			<xs:attribute name="mailSmtpHost" type="xs:string" use="optional"/>
+			<xs:attribute name="mailSmtpPort" type="xs:string" use="optional"/>
+			<xs:attribute name="mailUser" type="xs:string" use="optional"/>
+			<xs:attribute name="mailPassword" type="xs:string" use="optional"/>
+			<xs:attribute name="mailFromAddress" type="xs:string" use="optional"/>
 		</xs:complexType>
 	</xs:element>