Secondary Domain
A secondary domain is an additional domain, often a close variant of a company's primary domain name, registered specifically for sending cold outbound email at scale. It functions as a type of sending domain, purchased alongside others to spread volume and isolate deliverability risk from the main brand domain.
Why it matters for outbound teams
Buying several secondary domains lets an outbound team run dozens of mailboxes without ever touching the primary domain that customers and partners see. If a secondary domain gets burned, the team retires it and moves on without any impact on the core brand. This is standard infrastructure for any cold outbound program sending meaningful volume.
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