Inbox Rotation
Inbox rotation is the practice of distributing outbound sends across many mailboxes and sending domains rather than one, cycling through them so no single inbox sends a volume that triggers spam filters. It is a core deliverability tactic for cold email at scale.
Why it matters for outbound teams
Mailbox providers throttle or flag accounts that send high volumes of cold outreach from a single address, so spreading sends across dozens or hundreds of inboxes keeps per-inbox volume low and natural-looking. This is standard practice in tools like Smartlead and Instantly, which are built around managing large rotations. The tradeoff is that replies now land across just as many inboxes, which is the problem a unibox exists to solve.
See every reply in one place
Master Inbox pulls email and LinkedIn replies from every sending tool into one inbox. Free 7-day POC. Unlimited users on every plan.
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