SAP Internet Mail Gateway (BC-SRV-COM) 
Purpose
This component connects the R/3 mail system to the Internet. It enables R/3 users or R/3 applications to send electronic messages to Internet addresses or to receive them in the R/3 System. The connection is made using the standard protocol used in the Internet, SMTP (Simple Mail Transport Protocol).
Introduction notes
In addition to the SAP Internet Mail Gateway contained in the R/3 standard system, a
mailing program is also required for the connection to the Internet.If you protect your R/3 System with a firewall, you can regulate access to the Internet using a proxy. In this case, the connections are controlled using the
SAProuter.
Integration
The Internet Mail Gateway supplied by SAP is one way of connecting the R/3 mail system to the Internet:

The connection is made by RFC to the R/3 communication interface
SAPconnect. As a result, the SAP Internet Mail Gateway enables message to be sent from the
Business Workplace and directly from R/3 applications.
This documentation describes the
planning of the Internet link, the structure, the installation and the configuration of the SAP Internet Mail Gateway and contains notes on testing and on error analysis.