In the second half of 2021, Microsoft stopped supporting basic authentication for Exchange Web Services (EWS) to access Exchange Online. Basic authentication was replaced with modern authentication (based on OAuth 2.0). Please see Exchange Online deprecating Basic Authentication - Microsoft Lifecycle | Microsoft Docs for more details.
Starting from the 8.3.0 version Cayosoft Administrator uses only modern authentication and requires Exchange Online PowerShell Module (EXO V2).
Cayosoft Administrator does not explicitly force basic authentication for Exchange Online connection. It uses EXO V2 PoSh module which supports all modern authentication flows. EXO v2 performs the direct call to New-PSSession and uses basic authentication for transport reasons only to pass the Access Token in the HTTP headers according to HTTP Basic authentication protocol. It does not use basic authentication to pass clear text credentials. For details, please see Basic auth - Connect to Exchange Online PowerShell | Microsoft Docs.
The username/password isn't sent to the service using Basic, but the Basic Authentication header is required to send the session's OAuth token because the WinRM client doesn't support OAuth. We are working on this problem and will have more to announce in the future. Just know that enabling Basic on WinRM is not using Basic to authenticate to the service. Please see this Microsoft article for more details: Deprecation of Basic authentication in Exchange Online | Microsoft Docs.