How to handle bounce and invalid address management for cold lists?

Proper bounce management protects sender reputation and maintains list quality.

Hard bounces:

Permanent delivery failures (user doesn't exist, domain invalid)

Remove immediately after first occurrence

Add to permanent suppression list

Never attempt to send to these addresses again, even from new data sources

Soft bounces:

Temporary failures (mailbox full, server temporarily unavailable)

Retry a limited number of times (most tools handle this automatically)

After 3 to 5 consecutive soft bounces, treat as hard bounce

Track patterns to identify problematic domains

Suppression management:

Maintain a master list of bounced addresses across all campaigns

Check new data imports against suppression list before adding

Sync suppression across all sending tools and sequences

Monitoring:

Track bounce rates per campaign and over time

Investigate sudden spikes (data quality issue or blocklisting)

Aim for bounce rates under 2% for cold email

High bounce rates on purchased lists indicate poor data quality