Hi Florian,
ERMS push will only send the mail ID to BCM. Below is the sap help about ERMS push:
http://help.sap.com/saphelp_crm70/helpdata/EN/0e/6a22b86821468691bd5abb51dfd81e/content.htm
The action Push E-Mail to IC WebClient Agent needs to be add in your ERMS rule.
Hope this help!
Thanks,
Norman