Sending Domain
The domain emails are sent from. Cold senders use separate secondary domains to protect their primary brand domain's reputation from outbound volume.
A sending domain is the domain in the from address of an email. For cold outreach, the standard practice is to send from dedicated secondary domains — often close variants of the brand — rather than the primary company domain, so that any reputation damage from cold volume never touches the address employees rely on for everyday mail.
Each sending domain needs its own authentication (SPF, DKIM, DMARC), warm-up, and conservative daily limits, and is usually paired with several mailboxes feeding an inbox rotation. Treating sending domains as disposable, replaceable infrastructure — monitored for reputation and retired if they sour — is what lets a cold-email program scale without risking the core business domain.
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