need help with ssl errors for outbound emails

Hi all

I need help with a strange problem affecting a MDaemon 18.5.3 installation on recently upgraded Windows Server 2012 R2 virtual machine.

Everything worked fine until, some days ago, in the weekend, I installed a Root CA in my Windows Domain, precisley where it's installed MDaemon.

From that time, every email going out it's stopped by Amazon AWS's relay server (which we use to send emails) stating multiple causes.

I will post some logs:

02: (-- 250-email-smtp.amazonaws.com
02: (-- 250-8BITMIME
02: (-- 250-SIZE 10485760
02: (-- 250-STARTTLS
02: (-- 250-AUTH PLAIN LOGIN
02: (-- 250 Ok
03: --) STARTTLS
02: (-- 220 Ready to start TLS
Socket connection closed by the other side (how rude!)
Socket error 10053 - Connection abort.
Connection closed

or

02: (-- 250-AUTH PLAIN LOGIN
02: (-- 250 Ok
03: --) STARTTLS
02: (-- 220 Ready to start TLS
04: * SSL negotiation failed, error code 0x90317
04: * 176.34.134.214 added to temporary SSL white list, will retry delivery soon

when host is added to whitelist, every mail is going to be rejected because aws supports only TLS on port 587.

The thing I have noticed is that, every time an error for an outbound email is logged in MDaemon console, a SChannel error is logged in Windows Event Console. I will report one, they are all identical

A fatal alert was generated and sent to the remote endpoint. This may result in termination of the connection. The TLS protocol defined fatal error code is 10. The Windows SChannel error state is 10.

Needed to be said: an SChannel error was logged sometimes every 2 or 3 days, by Windows, purely randomly, even before CA deployment. And very very rarely one or two times it crashed the entire Windows Server, forcing it to reboot the virtual machine.

Please I need support.
Thanks!