Symptoms
FIP-FS proxy customizations that are configured for antimalware updates by using the Set-ProxySettings command in the Microsoft.Forefront.Filtering.Management.PowerShell snap-in are disabled after you install a cumulative update or a security update in Microsoft Exchange Server 2019.
Resolution
To fix this issue, install the following cumulative update:
Cumulative Update 14 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019