Phpmailer: Connects to remote SMTP server then gives "Could not connect to SMTP host"

[m0lmk]

I bit of a strange problem here. It looks like PHPMailer is connecting to my remote SMTP server and then decides to disconnect. Here's the code that I am using..

$mail = new PHPMailer;
$mail->isSMTP(); 
$mail->SMTPDebug = 3;
$mail->Host = 'mail.mydomain.co.uk';  
$mail->SMTPAuth = true;                               
$mail->Username = '[email protected]';                 
$mail->Password = 'mypassword';                          
$mail->SMTPSecure = 'tls';                           
$mail->Port = 587;                                    
$mail->setFrom('[email protected]', 'My Domain - No Reply');
$mail->addAddress($client['email']);    
$mail->addReplyTo($property['email']);

$mail->isHTML(true);                                  
$mail->Subject = 'Message subject';
$mail->Body    = $bodytexthtml;
$mail->AltBody = $bodytext;

And this is the debug message I get...

2016-08-15 13:02:53 Connection: opening to mail.mydomain.co.uk:587, timeout=300, options=array ( ) 2016-08-15 13:02:53  Connection: opened 2016-08-15 13:02:53  SERVER -> CLIENT: 220 mail.mailserver.com ESMTP Postfix (Debian/GNU) 2016-08-15 13:02:53    CLIENT -> SERVER: EHLO www.mydomain.co.uk 2016-08-15 13:02:53   SERVER -> CLIENT: 250-mail.mailserver.com 250-PIPELINING 250-SIZE 250-VRFY 250-ETRN 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN 2016-08-15 13:02:53   CLIENT -> SERVER: STARTTLS 2016-08-15 13:02:53  SERVER -> CLIENT: 220 2.0.0 Ready to start TLS 2016-08-15 13:02:53  SMTP Error: Could not connect to SMTP host. 2016-08-15 13:02:53 CLIENT -> SERVER: QUIT 2016-08-15 13:02:53  SERVER -> CLIENT: MIA#�8~��;���>� �$܈#´�K��S�������w ]M��5��E�|8D��(����k>)N+.��
S��D������S�M�I���l\x���D�Y=��Af&�#Q����'z��q�/($���Vc�G�#-/&�d��a�q�O!� �k�f"��pS���(��$�wEBS}y9s|��$]��a��|��ӾuE�(�����0Q��?�
�v��������>#M���4Kנ��'���W.�dž@(�#�PH.F�Sтs��\(�:U���b#�����d��9k
��Y��Uk����I)a�N����>�+���O��8��X�WtM����F��6sL��n#�#!����_��e���z�v��^�t$B!J8�;�%�aAC�;����{�
�h%ۏ�D]FZ��`:\�R�F�{���ČH i@�B��d�(N�a�̅7�f ��(�n�݀���-�nt{��Au������NF��!E@��b��rW�5(+Ž��p��sE�u����5N��g#4V��[��C�)��P�[g��OU�L[�@�c�H6���6_�C��Bu�� 2016-08-15 13:02:53 SMTP ERROR: QUIT command failed: MIA#�8~��;���>� �$܈#´�K��S�������w ]M��5��E�|8D��(����k>)N+.��
S��D������S�M�I���l\x���D�Y=��Af&�#Q����'z��q�/($���Vc�G�#-/&�d��a�q�O!� �k�f"��pS���(��$�wEBS}y9s|��$]��a��|��ӾuE�(�����0Q��?�
�v��������>#M���4Kנ��'���W.�dž@(�#�PH.F�Sтs��\(�:U���b#�����d��9k
��Y��Uk����I)a�N����>�+���O��8��X�WtM����F��6sL��n#�#!����_��e���z�v��^�t$B!J8�;�%�aAC�;����{�
�h%ۏ�D]FZ��`:\�R�F�{���ČH i@�B��d�(N�a�̅7�f ��(�n�݀���-�nt{��Au������NF��!E@��b��rW�5(+Ž��p��sE�u����5N��g#4V��[��C�)��P�[g��OU�L[�@�c�H6���6_�C��Bu�� 2016-08-15 13:02:53  Connection: closed 2016-08-15 13:02:53 SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting Message could not be sent.

Mailer Error: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

If I comment out "$mail->isSMTP();" then it works but does not send via my SMTP server.

Any idea where I should start to debug this?

Thanks.

[m0lmk]

Looks like I solved this one. The remote server was using an invalid certificate. I added this to my code and all works fine...

$mail->SMTPOptions = array(
  'ssl' => array(
    'verify_peer' => false,
    'verify_peer_name' => false,
    'allow_self_signed' => true
  )
);

I'll leave it here in case anyone else runs into this.

[Synchro]

As the docs say, while this stops the error messages, this is not a good solution - better to fix the certificate the server is using as otherwise it's just making you vulnerable to impersonation, forgery and MITM attacks.

[m0lmk]

Yes, good points Synchro.

I've updated the certificate on the server and removed the code but it was very useful for debugging.