If you type this in the CC-input field: "Your Name (your@email.com)" your@email.com you will endup with a bounce.
It seems roundcube is seeing the values between the " as an emailadress.
Reprodruce this error:
Typ in the CC-field: "Your Name (your@email1.com)" your@email2.com
And you'll get an error about email1.com
P.S. I tried to put this in the TRAC-system, but couldn't create a login.
Best regards, Pascal Nobus -- www.webservice.be