Do not use your primary business email ID or domain (the one you use for proposals, invoices, and day-to-day email) for cold outreach campaigns.
Why: Cold outreach can produce bounces when prospects change jobs or email IDs expire. High bounce rates can damage your primary domain's sending reputation — and push your transactional email into spam.
Best practice: Register a closely related domain (e.g. if your primary is getco.com, register getco.io or getcos.com) and use that for outreach. Forward it back to your main website so it looks legitimate to prospects.