This issue occurs when you configure the Alibaba Mail account on the Outlook client. When you use the Outlook client to receive emails, all emails on Webmail are deleted. In addition, when you make a self-service request on Webmail, the result indicates these emails are deleted by the POP protocol. You must check the default settings of the Outlook client.
Choose Account Settings > More Settings > Advanced. You may not select the Leave a copy of messages on the server option. If the option is not selected, the client will delete all emails on the server after the emails are received. We recommend that you select the option to prevent the emails of the mailbox are deleted by mistake.
To prevent emails from being deleted by mistake owing to improper settings on email clients, you can log on to Alibaba Mail Webmail to set the required options. Click Settings in the upper-right corner, choose Settings > POP Settings, select forbidden in the Allow No Email Receiving Software to Delete Emails.