I’ll answer your question. You don’t need another email, but you will have 2 different contracts under the same account. Everything you do, you will need to ensure you have the correct contract selected. You will not be able to combine points, so if you have a few days booked under each contact, you will not be able to merge the reservations. (Front desk is good about leaving you in the same room, but you will need to check out and back in).
It is not a problem if you are a logical thinker, and able to keep track of each contract in your head, which points you are planning to use, etc. If you are using the second contract for specific trips, it likely wouldn’t be difficult to track.