Outbound Glossary
Inbox rotation
Spreading a campaign across several mailboxes to stay under each one's limit. It raises volume, and it multiplies what you have to monitor.
Every mailbox has a safe daily ceiling, so a campaign that needs more volume uses several mailboxes and distributes the sending between them. Tools do this automatically once the mailboxes are connected.
The cost is hidden. Ten mailboxes means ten reputations, ten warm-up schedules and ten places a problem can start without you seeing it, and a single bad one drags the average. Rotation is a way to use capacity you have earned, not a way to get capacity you have not.