I'm trying to understand how apps such as greenhouse.io configure DNS for delegating email sending.
In short, assume I am a SAAS provider saas.com
and my customer is customer.com
. I've seen that it is possible to:
- Ask my customer to create a subdomain - say
saas.customer.com
and add DNS records for DKIM validation. The intent is that my SAAS can send emails fromsaas.customer.com
. - Once they add, I (
saas.com
) can send emails fromuser@saas.customer.com
.
I understand the above.
However, I also see that (especially for greenhouse.io), it's also possible to send with the From:
message header as user@customer.com
(and not just user@saas.customer.com
). This is somewhat surprising to me.
In summary, if I am authorized to send emails from a subdomain, and I use that subdomain to send with emails where from header is a parent domain (I understand that this is not the envelope sender) is this a valid use-case - or does this have possibilities of being marked as spam etc?
I'm using Amazon SES, if it matters.