How to Improve Inbox Delivery for Cold Emails from New Subdomains in GTM

Hi all, Newbie in the GTM world. Recently got new subdomains to cold email super targeted lists like 30-40 people max. While testing, most of them landed in spam. Would love some advice on how to consistently ensure emails lands in inbox? My emails will be personalized demos, so it's important that they are delivered to the inbox.