Core Issue
From Cisco Unity Express prompts, the connection to backup server is established and the backup server can response to ping, but the backup progress remains at 0 bytes. History.log shows this output:
Category: Configuration
Backup Server: ftp://x.x.x.x/backup/
Operation: Backup
Backupid: 2
Date:
Result: Failure
Reason: Connection to backup server failed: ftp://x.x.x.x/backup/ : returnvalue:6 Unable to connect to backup server.
Resolution
It is observed that if the FTP password contains a special character, it does not allow the backup. In order to resolve this issue, remove the special character from the FTP password. Also make sure that there are no routing problems in the network that can affect the FTP backup on Cisco Unity Express.