What are the consequences of non-compliance?

Consequences of non compliance escalate from warnings through increased filtering to outright rejection. Initial violations may trigger temporary filtering increases while providers assess whether problems are corrected. Sustained non compliance leads to more severe blocking.

Gmail's enforcement includes temporary failures (421 errors) during evaluation, increased spam folder placement, and eventual rejection (550 errors) for persistent violators. Yahoo similarly escalates from deferrals to blocking as violations continue.

Reputation damage from non compliance takes longer to repair than the time it takes to accumulate. A few weeks of violations can require months of clean sending to recover. The asymmetric nature of reputation damage makes prevention far preferable to remediation.