Sequences send from a pool of mailboxes, rotating automatically. Rotation spreads reputation risk, raises total capacity, and isolates problems. Rule of thumb: total daily volume ÷ 100 = mailboxes needed.
How rotation works
Assign multiple mailboxes to a sequence's sending pool. Each new prospect is pinned to one mailbox (the whole conversation stays on it — threading matters); new conversations distribute across the pool by capacity and health.
Sizing the pool
At 100–150 safe sends per warmed mailbox per day: 500/day needs 4–5 mailboxes, 1,000/day needs 8–10. Spread mailboxes across 2–3 sending domains so a domain-level issue doesn't halt everything.
Health-aware distribution
Rotation weights by health: an Amber mailbox receives fewer new conversations automatically; a Red one receives none. Recovery restores its share gradually.
Domain strategy
2–4 mailboxes per sending domain is the sweet spot. More mailboxes on one domain concentrates risk; one mailbox per domain multiplies DNS and warm-up overhead without much benefit.
