Sending rules and list practice
What is a suppression list?
Also called: do-not-email list, global unsubscribe list
A suppression list is a list of addresses you must never mail again: people who unsubscribed or complained, and addresses that hard bounced. It sits above every campaign and every imported list, so an address removed once cannot sneak back in through a new upload or a different tool.
The legal side is about opt-outs. In the US, CAN-SPAM requires commercial senders to honour an opt-out within ten business days; the mailbox providers' rules for bulk senders ask for two days.
The deliverability side is about bounces and complaints. Re-mailing an address that bounced or reported you is the fastest way to raise both rates.
Keep one suppression list per brand and check every list against it before sending, including lists in a new tool. Suppressing invalid addresses after verification stops them coming back when the same leads are exported again.
How SimpleVerifier handles it
SimpleVerifier does not hold your suppression list. Add the invalid file from each verification run to the suppression list in your sending platform so those addresses stay out.
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Sources
By SimpleVerifier Team · Last reviewed 2026-10-13 · All 50 glossary terms