> But even worse than that, the "confirm your email" email and the following "finish account setup" email came from two different sub-domains. Maybe this is just a new attempt to get around Google's spam filter, but it seems like the worst thing you could possibly do when sending emails.

Standard advice is to use one subdomain for "transaction" email (verification, invoices) and another for marketing

https://www.twilio.com/docs/sendgrid/onboarding/email-api/ev...