All emails into spam. Is the mistake sending from a domain without a website?

All my cold emails go to spam (checking on gmass). 10/10 mail-tester score. Separate 2 month old warmed up dotcom domain. Not in any spam list. All emails verified, including for spam traps. SMTP server with a dedicated IP. 100% emails go into spam. I was advised that sending email via a domain other than the main one ( having a subscribe form) is frowned upon by postal servers, and that`s why all emails go into spam. Is it the reason? I had been told before that it is good to send emails from a different domain to protect the main one of getting blacklisted so hence sending from a separate one. Anyway, all is placed into spam. Wth actually

submitted by /u/myshaka
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source https://www.reddit.com/r/Emailmarketing/comments/ixb3zu/all_emails_into_spam_is_the_mistake_sending_from/