protected xclient variable and added tests

examples/smtp_xclient.phps

@@ -29,7 +29,9 @@ $mail->Host = 'mail.example.com';
 $mail->Port = 25;
 //Whether to use SMTP authentication
 $mail->SMTPAuth = false;
-$mail->SMTPXClient = ['LOGIN' => 'yourname@example.com'];
+$mail->setSMTPXclientAttribute('LOGIN', 'yourname@example.com');
+$mail->setSMTPXclientAttribute('ADDR', '10.10.10.10');
+$mail->setSMTPXclientAttribute('HELO', 'test.example.com');
 //Set who the message is to be sent from
 $mail->setFrom('from@example.com', 'First Last');
 //Set an alternative reply-to address

src/PHPMailer.php

@@ -358,12 +358,11 @@ class PHPMailer
     public $AuthType = '';
 
     /**
-     * SMTP SMTPXClient command variables
-     * Options are NAME | ADDR | PORT | PROTO | HELO | LOGIN | DESTADDR | DESTPORT
+     * SMTP SMTPXClient command attibutes
      *
      * @var array
      */
-    public $SMTPXClient = [];
+    protected $SMTPXClient = [];
 
     /**
      * An implementation of the PHPMailer OAuthTokenProvider interface.
@@ -2005,6 +2004,29 @@ class PHPMailer
         return $this->smtp;
     }
 
+    /**
+     * Provide SMTP XCLIENT attributes
+     * Possible attributes are NAME, ADDR, PORT, PROTO, HELO, LOGIN, DESTADDR, DESTPORT
+     *
+     * @param string $name  Attribute name
+     * @param ?string $value Attribute value
+     * 
+     * @return bool
+     */
+    public function setSMTPXclientAttribute($name, $value)
+    {
+        if (!in_array($name, ['NAME', 'ADDR', 'PORT', 'PROTO', 'HELO', 'LOGIN', 'DESTADDR', 'DESTPORT'])) {
+            return false;
+        }
+        if (isset($this->SMTPXClient[$name]) && $value === null) {
+            unset($this->SMTPXClient[$name]);
+        } else if ($value !== null) {
+            $this->SMTPXClient[$name] = $value;
+        }
+
+        return true;
+    }
+
     /**
      * Send mail via SMTP.
      * Returns false if there is a bad MAIL FROM, RCPT, or DATA input.

src/SMTP.php

@@ -965,7 +965,7 @@ class SMTP
 
     /**
      * Send SMTP XCLIENT command to server and check its return code.
-     * Possible keys NAME | ADDR | PORT | PROTO | HELO | LOGIN | DESTADDR | DESTPORT
+     * Possible keys NAME, ADDR, PORT, PROTO, HELO, LOGIN, DESTADDR, DESTPORT
      * @return bool True on success
      */
     public function xclient(array $vars)

test/PHPMailer/PHPMailerTest.php

@@ -1191,6 +1191,25 @@ EOT;
         );
     }
 
+    /**
+     * Test SMTP Xclient options
+     */
+    public function testSmtpXclient()
+    {
+        $this->Mail->isSMTP();
+        $this->Mail->SMTPAuth = false;
+        $this->Mail->setSMTPXclientAttribute('ADDR', '127.0.0.1');
+        $this->Mail->setSMTPXclientAttribute('LOGIN', 'user@example.com');
+        $this->assertFalse($this->Mail->setSMTPXclientAttribute('INVALID', 'value'));
+        $this->Mail->Subject .= ': Testing XCLIENT';
+        $this->buildBody();
+        $this->Mail->clearAllRecipients();
+        self::assertTrue($this->Mail->addAddress('a@example.com'), 'Addressing failed');
+        $this->Mail->preSend();
+        self::assertTrue($this->Mail->send(), 'send failed');
+    }
+
+
     /**
      * Test SMTP host connections.
      * This test can take a long time, so run it last.