I have been trying to set up Roundcube with postfix and dovecot for a long time on a local vm LAMP server. I have managed to make it possible to log in to Roundcube and view local user emails I have sent from the linux command line, but I can't send any emails from Roundcube. So I'm wondering wether is it even possible to set up roundcube locally only.
As long as your SMTP server is working then Roundcube should be able to send emails, I guess you are getting an error of some kind?