PHPMailer установка на сервер

пытаюсь использовать phpmailer на сервере предприятия. Настраиваю следующим образом:

$mail = new PHPMailer;

$mail->SMTPDebug = 3;                

$mail->isSMTP();                                  
$mail->Host = 'gate';                  
$mail->SMTPAuth = false;                          
$mail->Username = '';      
$mail->Password = '';                    
$mail->SMTPSecure = 'tls';                        
$mail->Port = 25;                                
 
$mail->setFrom('[email protected]');
$mail->addAddress("$my_mail");    
$mail->isHTML(true);

Но получаю следующее:

        2021-06-22 13:24:38 Connection: opening to gate:25, timeout=300, options=array()
    2021-06-22 13:24:38 Connection: opened
    2021-06-22 13:24:38 SERVER -> CLIENT: 220 tret.in.ru ESMTP Postfix
    2021-06-22 13:24:38 CLIENT -> SERVER: EHLO srv
    2021-06-22 13:24:38 SERVER -> CLIENT: 250-tret.in.ru250-PIPELINING250-SIZE 157286400250-ETRN250-STARTTLS250-ENHANCEDSTATUSCODES250-8BITMIME250-DSN250-SMTPUTF8250 CHUNKING
    2021-06-22 13:24:38 CLIENT -> SERVER: STARTTLS
    2021-06-22 13:24:38 SERVER -> CLIENT: 220 2.0.0 Ready to start TLS
    2021-06-22 13:24:38 Connection failed. Error #2: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed [D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\SMTP.php line 468]
    SMTP Error: Could not connect to SMTP host.
    2021-06-22 13:24:38 CLIENT -> SERVER: QUIT
    2021-06-22 13:24:38
    2021-06-22 13:24:38
    2021-06-22 13:24:38 Connection: closed
    SMTP Error: Could not connect to SMTP host.

    Fatal error: Uncaught PHPMailer\PHPMailer\Exception: SMTP Error: Could not connect to SMTP host. 
    in D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php:2136 
    Stack trace: #0 D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php(1960): 
    PHPMailer\PHPMailer\PHPMailer->smtpConnect(Array) #1 D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php(1638): 
    PHPMailer\PHPMailer\PHPMailer->smtpSend('Date: Tue, 22 J...', 'This is a multi...') #2 D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php(1471): 
    PHPMailer\PHPMailer\PHPMailer->postSend() #3 D:\Server\data\htdocs\archive_documentation\forgotpassword\forgotpassword_query.php(52): PHPMailer\PHPMailer\PHPMailer->send() #4 {main} 
    thrown in D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php on line 2136

В чем может быть проблема? Может нужно какое-то почтовое приложение устанавливать для этого? До этого тестил это на openserver, все работало.

После удаления $mail->isSMTP();

    Sending with mail()
Sendmail path:
Envelope sender: [email protected]
To: [email protected]
Subject: Password
Headers: Date: Tue, 13 Jul 2021 10:45:55 +0000From: [email protected]: <vQYd7w7uiTPiyUnLEqgsK7jZEiQNK4OhB2UYnWSI@smk-srv>X-Mailer: PHPMailer 6.5.0 (https://github.com/PHPMailer/PHPMailer)MIME-Version: 1.0Content-Type: multipart/alternative; boundary="b1_vQYd7w7uiTPiyUnLEqgsK7jZEiQNK4OhB2UYnWSI"Content-Transfer-Encoding: 8bit
Additional params: [email protected]
Result: false
Could not instantiate mail function.

Fatal error: Uncaught PHPMailer\PHPMailer\Exception: Could not instantiate mail function. 
in D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php:1907 
Stack trace: #0 D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php(1640): 
PHPMailer\PHPMailer\PHPMailer->mailSend('Date: Tue, 13 J...', 'This is a multi...') 
#1 D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php(1471): 
PHPMailer\PHPMailer\PHPMailer->postSend() #2 D:\Server\data\htdocs\archive_documentation\forgotpassword\forgotpassword_query.php(51): 
PHPMailer\PHPMailer\PHPMailer->send() #3 {main} thrown in D:\Server\data\htdocs\archive_documentation\forgotpassword\PHPMailer-master\src\PHPMailer.php on line 1907