mail proxy
Mail proxy is proxy server that particularizes in e-mail transactions. The proxy server is a complete machine in front of the real mail server, which can be customized to provide services like email via Imap, virus scanning spam filtering ect.
Mail proxy server can be used a load balancer. If mails are routed through mail proxy server, the resource load is removed or reduced from the actual email server. Mail proxy server can also help to keep the actual email server behind firewall.
