How is reputation measured and scored internally by providers?

Mailbox providers use proprietary algorithms to calculate sender reputation. The exact formulas are never publicly disclosed, but we know the general signals they incorporate.

Gmail categorizes domain reputation as High, Medium, Low, or Bad in Postmaster Tools. Microsoft provides traffic light indicators through SNDS. These are simplified views of much more complex internal scoring systems.

Internally, providers weight factors like authentication pass rates, spam complaint percentages, spamtrap hits, engagement ratios, bounce rates, and behavioral anomalies. Machine learning models continuously adjust these weights based on emerging spam patterns.

The scores are dynamic. They update with every message you send and every recipient action. Think of it as a constantly recalculating credit score for your domain, where every transaction either deposits trust or withdraws it.