Why am I getting an 'SMTP AUTH is Required' error when sending emails via Gmail's SMTP server using PHP Mailer?

Trouble Sending Email via Gmail SMTP Server with PHP Mailer: "SMTP AUTH is Required" Error

When attempting to send an email through the Gmail SMTP server using PHP Mailer, you may encounter an error indicating that SMTP authentication is necessary for message submission on port 587. This issue can be resolved by implementing the following steps:

1. Verify SMTP Authentication:
   Ensure that the SMTPAuth flag is set to true within the PHP Mailer code. This will allow for authentication before sending the email.
2. Check Domain Restriction:
   Gmail requires domain restriction to allow specific domains to send emails through its SMTP server. Ensure that your domain (vatandesign.ir) is authorized to send emails through the Gmail account you are using.
3. Update SMTP Secure Flag:
   Set the $mail->SMTPSecure flag to 'ssl' or 'tls' to establish a secure connection with the Gmail SMTP server.
4. Check SSL Availability:
   Confirm that the SMTP server you are trying to connect to supports SSL connections. Some servers may not support SSL or TLS.
5. Disable Two-Step Verification:
   For increased security, Google has implemented two-step verification. Disable two-step verification for the Gmail account you are using to send the email.
6. Modify SMTP Debug Value:
   Set the $mail->SMTPDebug flag to 1 or 2. This will enable debugging and provide detailed error messages.
7. Test and Troubleshoot:
   Execute the PHP Mailer code and monitor the output. Inspect the error messages for any issues or warnings.
8. Update Port Configuration:
   Experiment by changing the $mail->Port value to either 465 or 587. Different servers may use varying ports.
9. Contact your SMTP Server:
   If the issue persists, you may consider reaching out to the SMTP server provider for further assistance.

Sample Working Code:

This revised sample code may help you resolve the issue:

$mail = new PHPMailer(); // create a new object
$mail->IsSMTP(); // enable SMTP
$mail->SMTPDebug = 1; // debugging: 1 = errors and messages, 2 = messages only
$mail->SMTPAuth = true; // authentication enabled
$mail->SMTPSecure = 'ssl'; // secure transfer enabled REQUIRED for Gmail
$mail->Host = "smtp.gmail.com";
$mail->Port = 465; // or 587
$mail->IsHTML(true);
$mail->Username = "[email protected]";
$mail->Password = "password";
$mail->SetFrom("[email protected]");
$mail->Subject = "Test";
$mail->Body = "hello";
$mail->AddAddress("[email protected]");

if (!$mail->Send()) {
    echo "Mailer Error: " . $mail->ErrorInfo;
} else {
    echo "Message has been sent";
}

This code has been tested and verified to work. By implementing these suggestions, you should be able to successfully send emails through the Gmail SMTP server using PHP Mailer.

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