Regarding MSP360 Backup for MS365, safely deleting the OST file is not possible because this solution specifically works with Exchange Online. Modifying or deleting the OST file during cloud backups may result in losing your cached data.

It's quite possible. MSP360 Backup for M365 backs up OneNote notebooks.

Hello Michel,

Please open a support case so that we can investigate the issue properly. If you have already opened a support case, please let me know its number.

Thank you

Utilizing an alternate password for data deletion adds an extra layer of security. To verify your alternate email address, a verification email should have been sent to the email address you provided. If you haven't received the verification email, please follow these steps to activate the email service in your provider account. Log in to https://console.msp360.com, navigate to 'Settings,' select 'Email Service,' and then follow the on-screen instructions. After that, you can re-add your alternate email address to verify it.