After deploying a cluster, time is not synchronizing properly.

The task that needs to be performed when time is not synchronizing properly after deploying a cluster is NTP configuration. In the Nutanix Multicloud Infrastructure (NCP-MCI) 6.5, Network Time Protocol (NTP) is used to synchronize the system time across all the nodes in a cluster. If the time is not synchronizing properly, it indicates that there might be an issue with the NTP configuration. Therefore, checking and correcting the NTP configuration would be the appropriate action to resolve this issue. The other options like DNS configuration, HA configuration, and SMTP configuration are not directly related to time synchronization in a cluster.