Go to: https://www.renderosity.com/dashboard/sitemail/settings and add a check mark as seen in screencap below then click Save Changes.

It might have something to do with Email Notifications being off by default if you never made any selection in this menu. "Receive email when sitemail sent" is a newly added feature.

Everything works as it should on my gmail account. Make an alias email and confirm it with Renderosity, if everything else fails. Emails will still make their way to your primary email.