I have a question regarding setting up domains in O365. We currently have a Hybrid setup, no mailboxes are in O365, only on-prem, all mail flows through our SPAM filter on-prem and MX still points to our Firewall. We were just notified that we needed to create a new domain and we were thinking that it would be easier to have all the mailboxes in O365. The question I have is can we have 1 domain only use O365 for mail routing and keep the other domain on-prem. We would also need to archive to a separate archiving service only from this new domain. Not sure how to go about this, so any advice would be great.