emails are going out as expected at the moment.
I was asking if you use your own SMTP but I checked and you are using our default system.
Some clients have reported that using their own SMTP is improving their email delivery rate. You can set up your own SMTP at the back office > Dashboard > Settings > Order email settings > Use SMTP?: Yes and fill in the required details.
You can read some more about SMTP here: https://booking.drivenot.com/en/knowledge-base/49-how-to-change-sender-email-and-name-for-order-emails
We have released Admin and Customer PWA mobile apps that allow for push notifications which have much better delivery and response rates. You can read more about PWAs here: https://booking.drivenot.com/en/documentation/87-progressive-web-app-pwa-for-admins
Hope this helps.