But like I said earlier, if you change it through the web interface it populates to the Outlook connector fine.
Yepp, confirmed. I didn't see the option to change the e-mail-address of the default account via webfrontend because it still shows my initial e-mail-address. However changing it there indeed is affection the Outlook Connector after restarting Outlook.
Thanks for the hint.
It is a work around but it should be fixed by Zimbra team.