Outlook Certificate errors with latest Windows updates

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We are using Avast Endpoint 170511-2
Ever since the Windows 10 Creators update to version 1703 we are getting a certificate warning message when using Outlook:
"'The server you connected to is using a security certificate that cannot be verified. Do you want to continue using this server ?"
The issue is that even after you select 'YES' the warning message comes up every time you do a Send/Receive.
I have found that if you open 'Manage Compute Certificates' and manually copy the 'Avast! Mail Scanner Root' Certificates from 'avast! Mail Scanner Cache' to the 'Trusted Root Certification Authorities' the warning message stops appearing....
.... until the next Windows Security update which seems to reset something and the warning message comes back again.

I hope a product update will fix this for good.

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I'm actually having a different issue in that the aVast mail scanner (build 1609 of endpoint) appears to not be passing certificates through properly as Outlook (2016, Office 365) reports that valid certs that already used by accounts in the client are issued by 'avast! mail scanner root' rather than the correct certificate authority.  You can just accept them and move on, but obvs this is some failure of the avast client to properly pass through certificates?