We use a service called SMTP.com to relay our notification emails.
As long as you have configured your buying site’s domain with a www CNAME record to point to investmentdominator.com as recommended you shouldn’t have to make any adjustments in regards to the email notification system.
However, if you are pointing your domain to our servers another way then you must configure a TXT record with a TXT Value of :
v=spf1 include:_spf.smtp.com ~all