For on-premises Tracker installations, one item is critical for best performance: a local mail server.
We're not suggesting you move your company mail server. Just install the mail server included with Windows and use a smart host to route to your actual mail server. The benefit of this configuration is that it minimizes the time it takes for Tracker email notification messages to be sent. During any action that triggers an email (e.g. adding/editing/tasking records), Tracker will wait for the notifications to be generated before the action is completed. A local mail server makes quick work of sending the messages and can then forward (relay) to your actual mail server in the background while other Tracker operations are happening.
Step-by-step instructions for setting this up can be found in this Knowledge Base article