I’m new to cold emailing and currently have a domain, the same as my website. However, so my main domain doesn’t get blacklisted or marked as spam permanently, should I use a subdomain (@mail.company.com) or get a completely new domain? (@mailcompany.com)

Here is a different use case for cold email. Not an agency or a coach. We are real estate investors and wholesalers. We are considering strategy and copy that might be successful in outreach to REAL ESTATE AGENTS to see if they know of any 'off market' fixer upper or distressed properties that need an investor to buy it for cash. Would this work well for this purpose? (what about outreach to probate and bankruptcy attorneys?)