When running that script by cron, an e-mail is sent (by cron) containing the script output.
It there is no output, no e-mail is sent.
Then it could be useful if the script where only outputting on error, that way no e-mail would be sent for successful backups.
When an error occurs the whole output would be printed (including previous successful/debug lines).
That setting would be disabled by default and configurable.
When running that script by cron, an e-mail is sent (by cron) containing the script output. It there is no output, no e-mail is sent. Then it could be useful if the script where only outputting on error, that way no e-mail would be sent for successful backups.
When an error occurs the whole output would be printed (including previous successful/debug lines). That setting would be disabled by default and configurable.