What is the significance of adding a '*' to a blacklisted email domain in Zendesk?

Adding a '*' to a blacklisted email domain in Zendesk is significant because it serves to block all email domains except those that are specifically whitelisted. By using the asterisk, it acts as a wildcard character, meaning that any email address from any domain that is not on the approved whitelist will be prevented from sending emails to the Zendesk support system. This effectively creates a protective barrier, ensuring that only trusted domains can communicate while denying access to all others. This feature is particularly useful in managing email correspondence and maintaining the quality of incoming requests by restricting unwanted or potentially harmful spam emails.