After removing Plesk from my server emails are no longer sent out through the websites. The server currently has 7 websites hosted on it. If a user tries to send an email through one of the forms or we try to email the user through the contact sections nothing happens. Also, the automated emails for signing up, placing an order and more are not sending either.
The software we are using for our websites are Magento, Wordpress, MediaWiki and Siwapp. From what I can understand this is not a software problem at the website level but a problem with our server configuration. We use an external mail server for our regular email communication which is working fine. I am able to provide root access to our server for the winning bid.
Plesk was removed due to a forced upgrade of PHP with the Plesk upgrade. Some versions of our software are not compatible with the newer versions of PHP, we do NOT want to upgrade PHP or reinstall Plesk. The server is running CentOS 5.