Yesterday I received a common question: does a subdomain have a different sender reputation than a domain?
Technically, yes.
They are two different domains, each with an email sending and receiving configuration, and, yes, they have separate deliverability metrics.
See the example below of a subdomain and domain reputation in Google Postmaster Tools:
However, there is a known “business” relationship between them, so if you send a high volume of messages, which could put the reputation of your primary domain at risk, I recommend using completely different domains.
