How to disable the WP mail (the letter)?

At my WP MU when a new sub-site is created - I (as a super admin) gets such email:

New site created by superadmin
Name: smth

Could you pls help me - how to disable this letter?

I don't need it so it is just spam for me...
May be this can help some how:
P.S.- @Jose could you help pls?