How can you group bounces by domain or ISP?

Grouping bounces by domain/ISP reveals patterns:

Domain extraction:

Parse recipient address. Extract domain portion (after @). Normalize variations (gmail.com, googlemail.com).

ISP mapping:

Group related domains: Gmail includes googlemail.com. Microsoft includes outlook.com, hotmail.com, live.com. Yahoo includes yahoo.com, aol.com, ymail.com.

Aggregation metrics:

Bounce rate per domain/ISP. Bounce type distribution. Error code frequency. Trend over time.

Pattern identification:

Provider-specific issues. Authentication problems at specific ISP. Reputation variations by destination. Content filtering differences.

Actionable insights:

Focus remediation on worst performers. Identify provider-specific configuration needs. Detect systemic issues early.

Domain grouping turns noise into signal. Patterns emerge when you aggregate by destination.