FIELD GUIDE
Clean your list before migrating: inactives, bounces and consent
Migration is the best time to clean, because you pay to move every address and a dirty list poisons a fresh account's reputation. Before exporting, deal with three things: inactive subscribers who never engage, bounced and invalid addresses, and consent you can no longer prove. Move a smaller, permissioned, deliverable list, and carry its suppressions with it.
Why clean before, not after
Cleaning before a move pays twice. First, most platforms bill by contacts or by sends, so every dead address you carry is either paid storage or wasted volume on the new plan. Second, and more important, a new account starts with no reputation, and the fastest way to ruin it is to import a list full of bounces and unengaged addresses and blast them on day one. A clean import means your first sends from the new platform go to people who actually open, which is exactly the signal a fresh sending reputation needs. Clean first, then map and import, following the migration checklist.
Deal with inactive subscribers
Inactive subscribers are the hardest call because they feel like assets. Define inactive concretely: no open, click or other engagement across a meaningful number of recent campaigns, not just a fixed number of days. Before deleting, run one re-engagement campaign asking them to confirm they still want your email, and keep only those who act. The rest should be suppressed, not migrated as active contacts. A large list that never engages does not make you money; it lowers your open rates, drags your placement, and inflates your bill. Moving platforms is the natural moment to stop carrying that weight into a fresh reputation.
Remove bounces and invalid addresses
Bounces and invalid addresses are the clearest cut. Remove every hard bounce: those addresses do not exist, and mailing them again from a new platform signals a careless sender immediately. Treat repeated soft bounces the same way once they persist. If a chunk of your list is old and never validated, consider a verification pass before import to catch typos, dead domains and spam traps, which are especially dangerous on a fresh account. The goal is that everything you import as an active contact is a real, deliverable address, and everything else moves across as a suppression so the new platform never tries it again.
Confirm consent, then carry suppressions
Consent is the part people skip and later regret. For each contact you should know where and when they opted in; if you cannot show that for a segment, it is a liability, not an asset, and a new platform will not vouch for permission you never had. Where consent is doubtful, re-permission before migrating or leave those contacts behind. Then carry your suppression data across: unsubscribes and bounces must import as suppressed on the new platform, or you will re-mail people who already left and undo the cleaning. Import active, permissioned contacts as active, and everything else as suppressions.
Questions people also ask
Should I delete inactive subscribers or just leave them?
Run one re-engagement campaign first, keep the people who respond, and suppress the rest rather than migrating them as active. Carrying a large unengaged segment lowers your open rates, hurts placement and inflates the bill on the new platform.
Do unsubscribes need to move too?
Yes. Export your unsubscribes and bounces and import them as suppressions on the new platform. If you skip this, the fresh account will mail people who already opted out, which both breaks trust and damages the reputation you are trying to build.