The only emails that get sent to guests automatically are confirmation of payment received emails when the deposit and balances have been paid by the guest.
The system will send email reminders to you when guest emails are due to go out.
For example when it is time to chase for the next payment. But in order for them to be sent, you will need to log into your reservation manager and send them manually.
The system does not automate guest emails for the simple reason of avoiding any emails going out accidentally due to an incorrect status change (as an example).
If you have overridden the default templates for the deposit received and balance received emails, the system will send your template, instead of the default.