The New Member Registration Email is sent either on a Per Level or Global Default basis.
If you want to prevent this email from being sent, you can use the options below.
There is an option to send a specific New Member Registration Email for each Level.
You can set if you want a specific email to be or not to be sent for the Level.
You can set the New Member Notification email for a Level as “Do NOT Send Email” and that email will not be sent.
That email can be set for each Level.
This is located in the Setup > Levels > *Click on Level Name* > Email Notifications section.
The global default New Member Registration email WishList Member sends when a member joins a Level can be found in the Advanced Options > Global Defaults > Email section of WishList Member
If the body of the email in Global Defaults is empty, then the email will not send.
But it has to be absolutely empty.