Acronis Cyber Cloud uses a Mailgun SMTP server for email notification delivery.
This article explains how to ensure all notifications from our side are received.
We recommend adding an SPF trust record for cloud.acronis.com on your mail server.
v=spf1 a mx include:cloud.acronis.com -all
See syntax documentation here.
Alternatively, you can white-list Mailgun's IP address dedicated for Acronis: 18.104.22.168.
If you have any additional questions, please contact Acronis Customer Central.