How do mailbox providers decide where to place emails?

Mailbox providers use complex filtering ecosystems built on authentication, sender reputation, engagement behavior, content signals, and historical patterns. These systems continuously learn from billions of messages.

If users often open and click your messages, future ones are welcomed. If they delete without reading or mark as spam, the tide turns against you.

Mailbox providers act like port authorities. They watch every captain’s track record before deciding whether your ship docks at the inbox pier or gets redirected to the spam quay.