Glossary
Blocklist
A list of senders, usually IP addresses or domains, that receivers refuse or treat with suspicion.
ValidReach Team · Updated 2026-10-26
In practice
Some are public DNS-based lists that a mail server queries when a connection arrives. Others are private lists kept by a mailbox provider. A single list rarely decides delivery on its own; providers weigh many signals.
A blocklist can also mean a list of addresses you choose not to send to, such as people who unsubscribed. Context makes the meaning clear.
Verification and sending
Keep your own suppression list of unsubscribed and bounced addresses so you never send to them again.