Domain Reputation
A measure used by email service providers to determine how trustworthy your domain is, impacting the deliverability of your emails.
The goal is to have High Domain Reputation in Google Postmaster Tools.
IP Reputation
The percentage of sent emails that could not be successfully delivered to the recipient's inbox.
The goal is to have High IP Reputation in Google Postmaster Tools. (If using a shared IP you don’t have full control of this).