Mails not being sent to people in CC

I think that you will need to put the CCADDR with the TOADDR when sending the mail:

s.sendmail(FROMADDR, TOADDR+CCADDR, msg.as_string())

You're correctly adding the addresses to your message, but you will need the cc addresses on the envelope too.

From the docs:

Note The from_addr and to_addrs parameters are used to construct the message envelope used by the transport agents.

You specified the CC entries in the message, but not in the envelope. It's your job to make sure that the message is also sent to the CC and BCC entries.