Sender Reputation
Sender reputation is calculated differently at all receivers to determine reputation. There are a few public sites that provide a glimpse into sender reputation that you can look up based on IP or sending domain, the most well known is Return Path's Sender Score.
What is Sender Score?
The Sender Score is an indication of the trustworthiness of an email sender's IP address and is used by email providers and filters to determine additional email filtering criteria. Just like a credit score is used by financial institutions to decide the terms of a loan, email providers use the Sender Score to determine the terms for filtering your emails.
Your Sender Score is an indication of inbox potential, but it's only one of many data points you need to determine how email providers may be junking, filtering, blocking, or bulking, your emails instead of delivering your email to inboxes. Your Sender Score isn't the same as your inbox placement rate.
If your Sender Score is low, email providers are more likely to apply filtering criteria to your entire IP address as well as each email campaign.
If your Sender Score is high, email providers are less likely to apply filtering criteria to your entire IP address, and will instead focus filtering criteria on each email campaign and on individual subscriber engagement.