Settings for Sending to the SAP System 
Use
SAP applications can specify their own senders for messages so that replies go back to the SAP System. If you use SAP applications that do this, you have to make additional settings in the mail system group. For more information, see the documentation for the relevant application.
Activities
The activities depend on which sender the SAP application specifies:
User
In order for replies to be sent to the SAP System, you have to make one of the following settings:
standard domain for the SAP System (transaction SCOT, Settings ® Default Domain) and do not assign an Internet address to the user. An Internet mail address in the form <user name>@<standard domain> is automatically generated for the user when he or she sends documents.
Business objects
In order for replies to be sent to business objects, you have to make the following settings:
Enter a standard domain for the SAP System (transaction SCOT, Settings ® Default Domain). An Internet mail address in the form <object type>.<object key>.%BOR
TRADER%@<standard domain> is automatically generated for the business object.The following applies for both senders:
If you convert the standard domain into the mail system group domain, you have to reconvert the domain for incoming Internet messages (replies). This cannot be done using the domain alone because then all messages would be routed to the SAP System. In the case of business objects, you can convert the address
*%BOR_TRADER%@domain back to *%BOR_TRADER%@standard domain, for example.