The domain name is the part of an e-mail address after the @ sign. It identifies a computer or network on the Internet. In this address, the domain name is adatum.com.
Some junk mailers change the sender name automatically for every message. If you add full e-mail addresses to your Blocked list, such as firstname.lastname@example.org, you may see spam the next day from email@example.com. What a nuisance.
The part of an e-mail address after the @ sign is called the domain. It identifies the computer or network on the Internet that was used to send the message. You'll be glad to know that by using a domain name in your blocked list, you can, for example, avoid all messages from "adatum.com." Add the domain name to your Blocked Senders List, and they're not spam, they're history.
On the other hand, if "@adatum.com" means mail to or from one of your customers, you don't want any of those messages to go to the Junk E-mail folder. Including the domain name on your Safe lists will allow all messages with that domain to pass directly to your Inbox.