You can change the Sender Email for New Member Registration emails for each Level within WishList Member.
You can edit that email in the Setup > Levels > *Click on Level Name* > Email Notifications section of WishList Member.
This is what appears after clicking the Edit Notifications button.
There is an Admin Info email set in the Advanced Options > Global Defaults > Admin Info section.
There is also the Global Sender Info Default which can be applied to all Levels in the Advanced Options > Global Defaults > Email section.
(The Sender Name and Sender Email are pulled from the Name and Email set in the Advanced Options > Global Defaults > Admin section)
You can also set the Sender Email Address for Email Broadcasts (if you use Email Broadcasts)
You can edit that email in the Administration > Email Broadcasts > *Click on blue Settings Button* section of WishList Member.
This is what appears after clicking the Settings button.