I wouldn't have though the OS would make any difference.
The SSL option in the Outlook email accounts should be unchecked and avast would then handle the secure connection.
Check that the avastUI, Real-time Shields, Mail Shield, Expert settings, SSL Accounts match up with your Outlook email account settings. The exception being if your email uses SSL (secure encrypted) protocol, then avast would detect that and this should be reflected in the Encryption column.
If they are the same, try deleting all the entries in the avast Mail Shield, Expert settings, SSL Accounts and reboot. That should recreate the entries.