The Catch-all alias

The catch-all alias account

is an email account that will catch any email sent to a non-existent email address under your domain name. Instead of sending the mail back to the sender, it will store it in the account assigned as a catch-all account.

Some hosting services do not support the catch-all alias. This type of alias allows spammers to send unsolicited email to random email addresses. This causes stress on mail servers, slowing down normal mail server functionality.