Hi Cyril,
Do you mean you do not want to give the license to newyork@mydomain.com but forwording the emails to newyork@mydomain.info?
If so, I suggest you do the following steps:
1. Add the newyork@mydomain.info account to External Contacts.
2. Create Distribution Groups for newyork@mydomain.com.
3. Add the newyork@mydomain.info to the related Distribution Groups(newyork.mydomain.com)
After that, the email sent to the Distribution Groups will be delivered to the additional users.
Thanks,
Jason Jiang