I'm still investigating about this matter but I think that these providers are putting 90% of emails coming from cpanel in Spam folder so Cpanel did the same with them
The majority of them are Microsoft products as you can see
If that is true, it makes perfect sense. And I am 100% backing cPanel's attitude.
I have several customers that rely on cPanel's email, and despite all the email configurations are 100% correct (SPF, DKIM, DMARC, the domains are not blacklisted, they are not sending newsletters, etc), despite all that, all their emails always end up on these providers Spam folders no matter what.
A colleague o mine that works in another company told me last week that he lost a customer just because he couldn't prevent their emails going to Spam.
I would say that this is NOT only a Microsoft's problem, but also Google.
For example, if you have your domain under management in Google Apps for Business, you can ask Google why your emails are going to other customers Gmail's Spam folder.
But if you have not, you cannot.
And if you try to find your way throught the pseudo Google support forums, you end up with solutions like: this happens because your customers have links in their email signature, even if the link is only the website from the same domain. WTF?..
The professional email services of Microsoft and Google are very important to this two companies.
I seriously believe action must be taken from companies like cPanel.
Because this is unfair and a dirty war.