We are using our own SMTP provider for branded emails. What we are finding as that all of our customers within a particular UK Government organisation are not receiving welcome/sign up emails. We’ve tried AWS SES, SendGrid and our own Gmail (part of our GSuite) all with no luck. All tests to contacts outside the organisation work (eg, personal gmail accounts etc)
Just to clarify, does the email come from Auth0 (but using our own SMTP) or does the email come from the email provider? We have Mailchimp and all of our marketing / newsletters get to this organisation with no issues… So we just want to confirm where the sign up emails originate from … if that makes sense?