What is Mailbox rotation (inbox rotation)?
Spreading one campaign's sends across many connected mailboxes so no single sender exceeds its daily limit.
Because each mailbox can only safely send 20–50 cold emails a day, reaching hundreds or thousands of prospects means many mailboxes. Rotation assigns each send to the next healthy mailbox with quota, respecting each one's gap and daily limit, so the campaign's total capacity is the sum of its senders. Adding mailboxes raises the ceiling; raising per-mailbox volume lowers deliverability.