The Default Address setting is used to determine what happens to mis-addressed messages, also called unrouted mail.
For example, a spammer might send ten or more messages based on your domain name to an assortment of common user names: admin@, contact@, contactus@, info@, support@, webmaster@, domain@, help@, sales@, etc. We've even seen spammers send to nonsensical users such a gh56sk29@ or 3c4f6h9s@. When there there is no mailbox or forwarder set up for that address, this is called unrouted mail.
The standard setting for the Default Address is for all unrouted email to be discarded by the LinkSky server with a message sent to the sender saying "No Such User Here."
You can see this setting by clicking on the Default Address icon in the Mail section of your cpanel home page.
This is the setting that LinkSky recommends and it is rare that you should ever need to change it.
The only other option is to Forward all of your unrouted mail to another email address. This is called a "catch-all" address and it's a very bad idea. Here's why:
Catch-alls can be very bad for your account as well as placing additional burdens on our email server and network.
When a spammer sends an email probe to a best-guess email address based on your domain, the messages NEVER bounce. Because the spammer doesn't get a bounced message, he assumes that he's hit several valid email addresses. Soon, hundreds, if not thousands of these best-guess email addresses based on your domain will be circulated world wide on spam lists where they will be bought and sold to thousands of spammers. When this occurs, your account and our server will be forced to process tens-of-thousands of junk mail messages daily all of which are sent to AnyAndEveryPossibleName@yourdomain.com. You may never see these messages, but I can assure you that our server will be using valuable resources to process them!
Again, catch-alls can be very bad for your account and they place additional burdens on our email server and network.
For more information on forwarding mail, see How can I create and use an email forwarder?
Thanks for help to keep your account and our email server free from abuse.