In what situations should the PHP version information be excluded from the X-Mailer header in email messages?

The PHP version information should be excluded from the X-Mailer header in email messages to prevent potential security risks. Exposing the PHP version in the X-Mailer header can provide attackers with information that may help them exploit vulnerabilities specific to that version. To prevent this, the PHP version information can be removed from the X-Mailer header by setting the X-Mailer header to a generic value without including the PHP version.

// Set X-Mailer header without PHP version information
$headers = 'X-Mailer: MyCustomMailer';