I have a request of setting up new CIFS shares but under different AD domain than an existing one.
Can I do that? What configurations should perform?
I'm pretty sure you can only do one SVM(vserver) to one AD domain.
Do the domains have a trust?
Will they allow you to create a new CIFS SVM for that domain?
Correct, one AD per vfiler (7-mode) or SVM (CDOT). If you wish to bridge the domains in the same SVM, you have to set up a trust to authenticate to the already configured domain.