You must login to the system to enter specific mail addresses or domains into your whitelist.

Click on Filter Rules

Then click on User Blacklist

To blacklist a specific mail address enter the address in the Sender Email: text box and click Add.

To blacklist a mail domain enter the domain in the Sender Domain: text box and click Add.

Blacklisting a spammer's address or domain can be ineffective because the address is often forged. Do not blacklist large well known domains - e.g. gmail.com