Outbound Glossary
Sending domain
A separate domain used for campaigns so a bad week never touches the domain your invoices and contracts go out from.
Outbound campaigns put a domain's reputation at risk in a way normal business mail does not. The standard answer is to send from a domain that is not your main one, usually a close variant, and keep your primary domain for mail that must always arrive.
The separation only works if it is real. Sharing one IP or one provider configuration across both can carry damage over, and so can having the same recipients mark both as spam. Treat the sending domain as expendable: if it burns, you replace it, and nothing you depend on stops.
Setting these up, warming them and replacing them when they burn is ongoing infrastructure, not a one-off task. RELAY™ includes it.