I am using SparkPost as my SMTP Server email provider. I verified my subdomain by adding SPF and DKIM as TXT records in Route53 on Amazon Web Services.
I use Discourse forum software. When I signed up as admin, the email arrived to the designated email address, but in Mozilla Thunderbird it says:
This message may be a scam.
The email address comes from a noreply@sub.mydomain.com (an email just for an example) address.
noreply@sub.mydomain.com is not an active email address. I mean, I didn't set it up.
Is there a way to tell SparkPost to receive emails from this address or to do something that it won't be counted as a spam email. I'm suer there are some checking that is done in email providers that check if the email address is legit.