Troubleshooting Tip: The Dropbox desktop app does not work when Deep Inspection is enabled on the FortiGate Firewall Rule

This behavior is typically due to Full SSL inspection being enabled. Dropbox uses end-to-end encryption(E2EE) to secure communications. Full SSL Inspection decrypts and re-encrypts traffic, which can break E2EE. For more information on the differences between SSL Certificate Inspection and Full SSL inspection, refer to this related article:

Technical Tip: Differences between SSL Certificate Inspection and Full SSL Inspection

The Dropbox team recommends whitelisting a list of domains in FortiGate. It is possible to find the list of official Dropbox domains here: What official domains does Dropbox use?.

To whitelist these domains in the SSL INSPECTION security profile under 'Exempt from SSL Inspection', follow these steps:

1. Create  addresses objects using the Dropbox Domain list What official domains does Dropbox use?  as FQDN:

2. Once each object has been created individually, add them into a single group:

3. Now that the address group is created, the deep inspection profile will be cloned since the default profile cannot be edited:
   

4. Add the group created above to the 'Exempt from SSL Inspection' in the 'SSL/SSH inspection' of the 'Clone of deep-inspection' profile under 'Security Profile' in the firewall.

5. Select 'OK' to save the changes. Test again on the Windows computer.