Confirmation emails not being sent

Confirmation emails are not being sent after successfully creating an appointment. Settings seem to be working otherwise – I can select the appointment date/time, enter information, submit, fill out and pay via Paypal, and the appointment shows up as active. I see an alert in the plug-in settings indicating that "[Appointments+] Either php curl is not installed or HTTPS wrappers are not enabled. Login with Google+ will not work." but I don't think that should be effecting the email. I've confirmed that Wordpress is sending out other emails so thats not the issue. Also note that selecting resend confirmation doesn't send the email either. Please help.

Thanks in advance,

Pieter