We have disabled the support for script through mails without authentication along with the up-gradation to Plesk v12. If a website uses a feedback or any mail sending script, then it has to be updated to ensure that it uses authenticated SMTP relay.
The traditional mail() function in PHP does not support SMTP authentication. Hence we recommend the use of PHPMailer class function, which is an open source and secure script for enabling the same:
PHPMailer Installation - http://phpmailer.worxware.com/index.php?pg=install
PHPMailer Sample code - http://phpmailer.worxware.com/?pg=examplebsmtp
The PHPMailer class files can also be found in the attached archive with this KB article. This attached archive has enough examples scripts ready for your help.
Please create a email id in your hosting account beforehand for using in SMTP authentication. Use mail.<your_domain.name> as SMTP server and use the full email id and password for SMTP authentication. You can use the standard SMTP port 25 for the same.
If your domain uses Gmail service, then please use smtp.gmail.com as SMTP server and port 465 for connection. Also make sure to enable SSL in PHPMailer through inserting the following code -
$mail->SMTPSecure = "ssl";
Also don’t forget to enable IMAP and POP access for the mentioned Google apps account and enable access for less secure apps, as shown in the screenshot bellow.
Important: Please make sure not to use the visitor's email id from the feedback form input in 'From' field of the email generated. Due to email server's security settings, emails from remote domains will not be relayed through authenticated SMTP. So use an valid email id from your own domain in the from field of the generated email and pass the visitors email id as information filed in generated message body.
If your website is built around Joomla CMS then you use it's built in SMTP configuration feature for configuring authenticated SMTP for your website. Please follow the links bellow for you version of Joomla deployment -
Joomla 2.5 - http://www.inmotionhosting.com/support/edu/joomla-25/how-to/configure-email-over-smtp
Joomla 3 - http://www.inmotionhosting.com/support/edu/joomla-3/server-settings/change-email-settings
For WordPress, it requires a plugin for enabling SMTP configuration feature.
Please get the required plugin from - https://wordpress.org/plugins/wp-mail-smtp/