Moving Email Sending to SparkPost (Bird): Suppressions, Unsubscribes and a Clean First Send

Bird starts with an empty suppression list. It records hard bounces and complaints as they happen on its platform, but your old provider's history doesn't come with you. Carry it across, verify the remaining addresses, and the first sends from your new SparkPost setup won't relearn bounces your old provider already knew about.

Sources, read 2 November 2026: Bird's email suppressions guide (formerly SparkPost's suppression list docs), its acceptable use summary and the full Acceptable Use Policy, and the bounce classification codes page.

How Bird suppresses

Event	Record	Blocks
Hard bounce (including out-of-band)	hard_bounce	All mail, transactional included
Spam complaint	complaint	Non-transactional only
Added by you	manual	All mail
Soft bounce, deferral, send-side rejection	None	Nothing
Unsubscribe	Stored as a preference, not a suppression	Marketing per your preferences

Two details matter in a migration. Suppressions are per workspace, so if you split marketing and product mail into separate workspaces, each needs its own history. And API keys can't remove complaint records (only signed-in dashboard users can), which protects you from a script that accidentally clears them.

Step by step

1. Export from the old provider: hard bounces, complaints, unsubscribes, and any manual blocks. The bounced email extractor turns raw bounce messages into a list if all you have is a mailbox of bounces.
2. Merge and lowercase. Bird lowercases addresses; the suppression list merger combines and dedupes exports from several tools.
3. Add bounces and complaints as manual suppressions in each workspace that sends. Manual records block all mail, which is stricter than a complaint record; for complaint addresses you still want to send receipts to, check the record type before adding.
4. Import unsubscribes as preferences, since Bird stores them separately.
5. Verify the active list on the verify page and add invalid results to the manual suppressions.
6. Warm the new sending setup with your most engaged, verified recipients before full volume; the email warmup schedule has a ramp.

What verification can't settle

Bird's policy is about consent as much as bounces: it names purchased, rented or scraped lists that don't comply with applicable law as prohibited. A verified list can still break that rule. On the technical side, catch-all domains accept every address so a single mailbox can't be confirmed, and Microsoft consumer mailboxes (outlook.com, hotmail.com) often don't answer single-mailbox checks reliably; those come back risky or unknown. Send them after the warm-up. Suppression list covers what belongs on yours.

Where SimpleVerifier fits

Verify the list before the switch on the verify page; the first 100 checks are free with a Google sign-in. Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off, and includes API calls for checking addresses at signup before they reach your sending platform. See pricing.