Here's how to set up notifications for reps that are assigned to a deal:
Go to Settings > Workflows
If you want the notification to go out when you assign an originator, expand the "Deal Originators Updated" section; or if you want the notification to go out when you assign a closer, expand the "Deal Closers Updated" section
Check "Notify Originators" or "Notify Closers" to send a push notification
Check "Trigger Webhook" to send the deal data to your own Zapier/Make/n8n workflow where you can send an email or take any other action.