I used to run my own mail server and had no trouble with deliverability for about 15 years. In the last 12 months it became so bad with certainly email provider

I used to run my own mail server and had no trouble with deliverability for about 15 years. In the last 12 months it became so bad with certainly email providers (I am looking at you Microsoft and Yahoo) that I was forced to change over to a dedicated email service (I went with luxsci). It would appear that some of the large email companies have effectively outsource spam filtering to the email service providers (email from one of the known service provider == good - everyone else == drop 1 in 20 emails randomly). This means that in practice it is impossible to run your own email server anymore if you care about deliverability.