Email Notification on Checked In/Reservation/Checkout.
Make sure, we have email account configured correctly in FrontDesk, in order to send an email while guest check in. Check FAQ: How to configure email account in eZee?
Step 2: Create email template
Path: eZee FrontDesk configuration >> "Configuration" Tab >> Select Letter Template.
After configuration with email template, Map that email template on "CheckIn" process option.
Path: eZee FrontDesk configuration >> "Advance Configuration" Tab >> "Notification" option