I think there needs to be a proper SMTP setup under "system settings > email" to allow modx to send emails... do you have that? Or do you have any Quip specific error messages in the error log?
Are other mail functionalities working with your installation? For example, try setting up a new user, enter your mail address and then check send password by mail. In this way, you can check whether the MTA of you server is working.
Actually, I have the same problem. My installation can send mails, but quip does not. Might be a bug.