Move Site to VPS server and get PHP mail working

I am currently hosting a joomla site on a shared hosting account with Godaddy. I also use godaddy to manage my domains. I was dissatisfied with Godaddy speed on there server so I purchased a VPS from VPSLAND.com. When I migrated my website over to their VPS, I am now unable to receive any email from the site. Right now you can register on the site and it is supposed to send an automated response to activate your account. I also have a contact form module that will not send after the move to the VPS. I am not sure about any of the DNS settings that should or shouldn’t have been change, or about DNS or MX records. I would like someone that is familiar configuring a VPS and knowledgeable on how to set up PHP mailing functions to fix this issue for me. I am pretty sure that this is a simple fix if you know what you are doing. I will be providing SSH access, FTP access, and control panel access to do what is needed. This VPS is running a Plesk control panel.