Manually reload proxy:
systemctl status zimbra-sccfd
zmprov modifyServer `zmhostname` +zimbraSSLUseLetSCrypt TRUE zmcontrol enable sccfd && zmcontrol start sccfd zimbra sccfd
(Note: In modern Zimbra builds, these settings are often abstracted into the Global Admin UI under Configure > Global Settings > Antivirus). Global Settings >
zmcontrol restart sccfd