What’s the best way to export/import suppression lists?

Suppression list transfer is critical. Failing to import suppressions means emailing people who bounced, unsubscribed, or complained, damaging your reputation immediately.

What to export:

• Hard bounces: Invalid addresses that will bounce again
• Unsubscribes: People who opted out (legally required to honor)
• Complaints: People who marked you as spam
• Soft bounces: Addresses with persistent delivery issues
• Manual suppressions: Any addresses you've blocked for other reasons

Export process:

• Most ESPs provide suppression export in account settings or via API
• Export as CSV or JSON with email addresses and suppression reason
• Include timestamps if available
• Verify export is complete (compare counts)

Import process:

• Import to new ESP before sending any email
• Verify suppression categories map correctly
• Confirm import completed successfully
• Test that suppressed addresses are actually blocked

Ongoing sync:

• During parallel operation, sync suppressions between ESPs
• New bounces/unsubscribes on old ESP should suppress on new ESP
• Automate if possible via API integration

This is the list of ships banned from port. Letting them dock anyway gets you flagged by harbor authorities.