Make Settings in the R/3 System 
Purpose
Various settings are made in the R/3 System, which are divided into two groups:
The following graphic shows what purpose the individual settings have:
Process Flow
Next make the system settings:

The user settings are prerequisites so that R/3 users can send and receive Internet messages. You can make these settings at any time - even during the production operation. They must however be made for all test users.