There are two methods block a sender, the first method is to access your Netwindy webmail, from within setting > Blocked and Allowed Senders you can specify Blocked Senders and Domains the formats supported are as follows: user@tld.com or @tld.com
The second options is supported with Zimbra connector and Microsoft Outlook. From within Microsoft Outlook you can right click on any email from within your inbox and Block Sender, this will set the sender of the email to a blocked state.
Note: All Netwindy Enterprise mail servers use advanced spam controls (Powered by MagicSpam) with adaptive filtering. The filters outlined in this document work independently of MagicSpam filters.