A component of Microsoft Exchange Server that enables Exchange to send and receive Simple Mail Transfer Protocol (SMTP) mail to foreign SMTP mail systems such as the Internet. Post Office Protocol version 3 (POP3) clients can use Internet Mail Service to send and receive e-mail.
Internet Mail Service can use the SMTP backbone of the Internet for connecting Exchange sites. Many sites have existing Internet connections that can be used for this purpose. One advantage of Internet Mail Service over Site Connector is that you can schedule Internet Mail Service to route messages at different times or intervals. One disadvantage is that this routing can produce a bottleneck because all messaging traffic flows through one server in each site.