To back up to Acronis Cloud Storage, outbound connections over the ports 443, 44445, and 55556 must be allowed on the machine where an Acronis agent is running.
Windows Firewall allows all outbound connections by default. You need to create new rules only if the connections are blocked by a personal or corporate firewall.
In many cases, it is acceptable to allow connections to any host/IP address. If you want to allow connections only to specific hosts/IP addresses, do the following:
To check the connections, use the telnet command or Acronis Cloud Connection Verification Tool, as described in the Acronis Knowledge Base article https://kb.acronis.com/content/4350.