e-mail server
server that can receive, forward, hold and send e-mails
Mail submission agent
computer program or software agent that receives electronic mail messages
mail delivery agent
software that routes e-mail to its destination
Microsoft Exchange Server
calendaring and mail server developed by Microsoft that runs exclusively on the Microsoft Windows Server product line
Smart host
type of email server
message transfer agent
software that transfers electronic mail messages from one computer to another using SMTP
Exim
mail transfer agent