To remove DualShield MFA from OWA, run the following commands in the Exchange Management Shell
Get-OwaVirtualDirectory | Set-OwaVirtualDirectory -AdfsAuthentication $false -BasicAuthentication $true -DigestAuthentication $true -FormsAuthentication $true -WindowsAuthentication $true -OAuthAuthentication $false Get-EcpVirtualDirectory | Set-EcpVirtualDirectory -AdfsAuthentication $false -BasicAuthentication $true -DigestAuthentication $true -FormsAuthentication $true -WindowsAuthentication $true