PHPMailer: SMTP Error: Could not connect to SMTP host

Question

I've used PHPMailer on several projects but now I'm stuck. It gives me the error:
SMTP Error: Could not connect to SMTP host.
I've tried sending email from Thunderbird and it works ! But not through PHPMailer ... Here are the settings from Thunderbird:

Server name: mail.exampleserver.com
Port: 587
Username: [email protected]
Secure Authentication: No
Connection Security: STARTTLS

I've compared these with the server at my last project where I used PHPMailer and they were:

Server name: mail.exampleserver2.com
Port: 465
Username: [email protected]
Secure Authentication: No
Connection Security: SSL/TLS

My php code is:

 $mail = new PHPMailer();
 $mail->IsSMTP(); // send via SMTP
 $mail->Host = SMTP_HOST; // SMTP servers
 $mail->Port = SMTP_PORT; // SMTP servers
 $mail->SMTPAuth = true; // turn on SMTP authentication
 $mail->Username = SMTP_USER; // SMTP username
 $mail->Password = SMTP_PASSWORD; // SMTP password
 $mail->From = MAIL_SYSTEM;
 $mail->FromName = MAIL_SYSTEM_NAME;
 $mail->AddAddress($aSecuredGetRequest['email']);
 $mail->IsHTML(true); // send as HTML

Where I am wrong?

Kirkwood

For those of you getting this in October 2021, please see this: #69413723 – Widen

Answer 1

Since this questions shows up high in google, I'd like to share here my solution for the case where PHP was just upgraded to version 5.6 (which has stricter SSL behavior).

The PHPMailer wiki has a section on this:

https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting#php-56-certificate-verification-failure

The suggested workaround is including the following piece of code:

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

This should work for PHPMailer 5.2.10 (and up).

Note: Obviously, and also as suggested in that wiki, this should be a temporary solution!

The correct fix for this is to replace the invalid, misconfigured or self-signed certificate with a good one.

Millymilman

This is the best answer for those struggling with localhost mailing and facing self signing issues. – Variety

Agreed! This is the best solution for those in a development environment. Just wrap that code in an if statement to check for environment type. If development environment, use that code, else let the the server worry about the certification. – Greatnephew

Best solution, after hours of wrecking my brain with all sorts of PHPMailer code parameter changes, it's ended up being a bug or incompatibility with newer PHP version. I'm now sending with localhost on my local dev environment. Well done Marten! – Ghetto

Massive thank you! Have been searching two days for a solution. – Kashakashden

Side note: I had my LetsEncrypt certs set wrong in Postfix. It must be fullchain.pem and privkey.pem, – Kashakashden

Works perfectly on localhost – Vagabond

This was very helpful. Thanks – Gromme

This breaks Gmail's XOAUTH2. If you're having trouble connecting check here: #30372410 – Netti

It didn't work for me, my PHPMailer is 5.5; – Yates

Answer 2

In my case it was a lack of SSL support in PHP which gave this error.

So I enabled extension=php_openssl.dll

$mail->SMTPDebug = 1; also hinted towards this solution.

Update 2017

$mail->SMTPDebug = 2;, see: https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting#enabling-debug-output

Pouch

Enabling this PHP extension (WAMP menu option) was what I needed. Thank You. – Quantify

You are my hero. I've been struggling with e-mails on my localhost for hours now, but this solved all my problems! – Collie

How did you enabled this extension? @Pouch – Exhibitionist

How I can to enable the extension=php_openssl.dll in GoDaddy Hosting? Thank's – Libation

Answer 3

Your problem is most likely this

Connection Security: STARTTLS Connection Security: SSL/TLS

Those are 2 different protocols, are you using the correct one, whatever one you're using in Thunderbird needs to be used.

Try setting the variable:

// if you're using SSL
$mail->SMTPSecure = 'ssl';
// OR use TLS
$mail->SMTPSecure = 'tls';

Iceman

Answer 4

I had a similar issue and figured out that it was the openssl.cafile configuration directive in php.ini that needed to be set to allow verification of secure peers. You just set it to the location of a certificate authority file like the one you can get at http://curl.haxx.se/docs/caextract.html.

This directive is new as of PHP 5.6 so this caught me off guard when upgrading from PHP 5.5.

Jittery

I'm in the same issue, using PHP5.6 if I put peer verification set to false in phpmailer emails goes to spam folder, Any idea how can I set the certificate path ? where to get the certificate ? in Debian 8 VPS – Fugleman

Thx. For me that has worked. That is: cd /etc/php5 && wget curl.haxx.se/ca/cacert.pem && echo "openssl.cafile = /etc/php5/cacert.pem" >> /etc/php5/apache2/php.ini – Yerga

Answer 5

I had the same problem and it was because PHPMailer realized the server supported STARTTLS so it tried to automatically upgrade the connection to an encrypted connection. My mail server is on the same subnet as the web server within my network which is all behind our domain firewalls so I'm not too worried about using encryption (plus the generated emails don't contain sensitive data anyway).

So what I went ahead and did was change the SMTPAutoTLS to false in the class.phpmailer.php file.

/**
 * Whether to enable TLS encryption automatically if a server supports it,
 * even if `SMTPSecure` is not set to 'tls'.
 * Be aware that in PHP >= 5.6 this requires that the server's certificates are valid.
 * @var boolean
 */
public $SMTPAutoTLS = false;

Lovato

Thanks. You don't need to edit the base class to change this though, just do $mail->SMTPAutoTLS = false; – Abuttals

Answer 6

does mail.exampleserver.com exist ??? , if not try the following code (you must have gmail account)

$mail->SMTPSecure = "ssl";  
$mail->Host='smtp.gmail.com';  
$mail->Port='465';   
$mail->Username   = '[email protected]'; // SMTP account username
$mail->Password   = 'your gmail password';  
$mail->SMTPKeepAlive = true;  
$mail->Mailer = "smtp"; 
$mail->IsSMTP(); // telling the class to use SMTP  
$mail->SMTPAuth   = true;                  // enable SMTP authentication  
$mail->CharSet = 'utf-8';  
$mail->SMTPDebug  = 0;   

Nameplate

Answer 7

Followed code worked for me:

$mail = new PHPMailer(true);

$mail->isSMTP();// Set mailer to use SMTP
$mail->CharSet = "utf-8";// set charset to utf8
$mail->SMTPAuth = true;// Enable SMTP authentication
$mail->SMTPSecure = 'tls';// Enable TLS encryption, `ssl` also accepted

$mail->Host = 'smtp.gmail.com';// Specify main and backup SMTP servers
$mail->Port = 587;// TCP port to connect to
$mail->SMTPOptions = array(
    'ssl' => array(
        'verify_peer' => false,
        'verify_peer_name' => false,
        'allow_self_signed' => true
    )
);
$mail->isHTML(true);// Set email format to HTML

$mail->Username = 'Sender Email';// SMTP username
$mail->Password = 'Sender Email Password';// SMTP password

$mail->setFrom('[email protected]', 'John Smith');//Your application NAME and EMAIL
$mail->Subject = 'Test';//Message subject
$mail->MsgHTML('HTML code');// Message body
$mail->addAddress('User Email', 'User Name');// Target email


$mail->send();

Eggshaped

I was skeptical, but this got it working. I think Gmail needs the SMTPOptions set as mine wasn't working without it. – Chaney

Answer 8

$mail->SMTPDebug = 2; // to see exactly what's the issue

In my case this helped:

$mail->SMTPSecure = false;
$mail->SMTPAutoTLS = false;

Corney

Answer 9

I recently dealt with this problem, and the cause of the problem turned out to be that the root certificate on the SMTP server that I was connecting to was the Sectigo root certificate that recently expired.

If you're connecting to the SMTP server by SSL/TLS or STARTTLS, and you've not changed anything recently in the environment where your PHPMailer script is running, and this problem suddenly occurred - then you might want to check for an expired or invalid certificate somewhere in the certificate chain on the server.

You can view the server's certificate chain using openssl s_client.

For SSL/TLS on port 465:

openssl s_client -connect server.domain.tld:465 | openssl x509 -text

For STARTTLS on port 587:

openssl s_client -starttls smtp -crlf -connect server.domain.tld:587 | openssl x509 -text

Tyika

Answer 10

Well this is really old but I still want to share my solution. If you are using phpmail with an local server like xampp turn off your antivirus. That solved it for me :)

Nissen

Answer 11

Since this is a popular error, check out the PHPMailer Wiki on troubleshooting.

Also this worked for me

$mailer->Port = '587';

Dripstone

Answer 12

I had a similar issue. I had installed PHPMailer version 1.72 which is not prepared to manage SSL connections. Upgrading to last version solved the problem.

Presidium

Answer 13

In my case in CPANEL i have 'Register mail ids' option where i add my email address and after 30 minutes it works fine with simple php mail function.

Cladding