Yes, you’re right. But to be honest, it only took me four weeks of perseverance and a few mails to the administrators of spam lists and I had no more problems with receiving and sending mail.
If you set up your mail server correctly and also enter a postmaster address, you will be informed of any problem, no matter how small, and can address it promptly.
I was surprised at how quickly and, above all, helpfully the staff at the spam list providers respond when you write to them politely and, if necessary, ask for more background information and best practices.
It was definitely worth it for me and I would do the work and build up the knowledge again at any time. As a result, you have maximum freedom in configuration and extensive options for customizing your own workflow in dealing with emails.
I also use Mailcow with three domains (one business). No problems with it from day one. Updates run regularly and smoothly like clockwork. I am happy to recommend it to others.