Managing an email server’s reputation is a constant struggle. Blocklists and ISPs can cause havoc for sending emails.
Reputation is built up over time based on how much of a “good actor” your email server is.
Sender Score is an option for checking sender reputation. The original site appears to request contact information, but the report seems to be able to be accessed just by going to a known URL:
Microsoft’s Smart Network Data Service (SNDS) can be used to monitor IP reputation with Microsoft receivers. [link]