Currently some users are experiencing an issue where their notifications are sent from the default site name rather than from their domain name. We're aware of the issue and are currently gathering more information regarding this matter.
In the meantime, you can do the following to resolve the issue:
Un-assign your domain.
Rename your site.
Assign your domain back to the site.
This article is credited to the Wix team - https://support.wix.com/ and we thank them for that!