By default, Helpdesk add-in would allow processing of any emails to support cases. However, if your support policy is only confined to customers from know or trusted companies or domains, you could configure Team Helpdesk to only process helpdesk related activities and workflow from emails sent from admin specified domain names. And emails from outside the trusted domains would be skipped. To implement this selective processing policy, the manager needs to define such list of trusted domains under Helpdesk Manager > Callers List > Company tab.
By default this selective processing from trusted domains is not enabled. To enable, go to Helpdesk Manager > Advanced Options > General tab and check the option ‘Only process incoming emails from domain names listed under Companies List‘.
So, when you or other technicians try to generate a new case from an email send from a unlisted domain, Helpdesk add-in would not process and instead a popup message would be shown that the email sender domain is not trusted. And if Helpdesk add-in was monitoring a mailbox (support account for example), and when a new email is received from unlisted domains (e.g., not in the Helpdesk Manager > Company list), the email would be moved to a subfolder called ‘Unlisted Domain Emails‘ for your references.