Stop crontab sending mail for backup script?

https://crontab.guru/#30_9_*_*_0

Select an editor on Vim or Vi

select-editor

To disable a specific crontab entry just capture all of the output of the command and either direct it to a file or to /dev/null.

30 * * * * notBraiamsBackup.sh >/dev/null 2>&1

Set MAILTO variable

You can set MAILTO=”” variable at the start of your crontab file. This will also disable email alert. Edit/Open your cron jobs:
$ crontab -e
At the top of the file, enter:
MAILTO=""
Save and close the file.