Exchange Email: How to block senders that you don’t want to receive email from them?

OWA

1. Click on the Options link at the top right of the window and then click See All Options...
2. Click Block or Allow on the left pane.
3. Add email address under Blocked Senders.
   

Outlook 2010

1. On the Home tab, in the Delete group, click Junk, and then click Junk E-mail Options...
2. Add email address under Blocked Senders.
   

Outlook 2007

1. From your Inbox, in the Actions menu, point to Junk E-mail and then click Junk E-mail Options.
2. Add email address under Blocked Senders.

Additional Notes:

1. Block sender's email address should not be put in your Contacts.
2. If you want to block sender with the "@ust.hk" email domain, you will need to use Inbox Rules.