Mistake: no suppression list, so you re-mail opt-outs and closed-lost

Mistake: no suppression list, so you re-mail opt-outs and closed-lost
Without a central suppression file, the next campaign re-imports people who already unsubscribed, replied 'not interested,' or are existing customers. Re-mailing an opt-out is the fastest route to a complaint — and in some regions, a fine.

The fix: maintain one global suppression list and check every import against it. Smartlead and Lemlist support account-level block lists; export unsubscribes and not-interested replies into it after every campaign. Add competitor and customer domains too.

Pros / Cons of a global suppression list:
— Pro: kills the worst complaint source — re-mailing opt-outs
— Pro: keeps you on the right side of CAN-SPAM/GDPR
— Con: must be maintained and synced across tools
— Con: easy to forget after a campaign ends

Verdict: 5/5. The single highest-leverage list you'll never send to.

Who it's for: anyone running campaign 2 without scrubbing against campaign 1.