- Outlook 2010 lets you block senders by email address, domain, and even subdomain.
- To block a sender, right-click on their email and choose "Junk > Block Sender": Outlook will confirm that "The sender of the selected message has been added to your Blocked Senders List, and the message has been moved to the Junk E-mail folder" (and will automatically do so in the future).
Tip: if you accidentally blocked someone, go to your Junk E-mail folder to find that message, right-click on it, and choose "Junk > Never Block Sender": Outlook will confirm that "The sender of the selected message has been added to your Safe Senders List". Manually move that email back to your inbox or another folder (Ctrl+Shift+V), it isn't automatically retroactive.
- To add a domain to your blocked senders list, right-click on an email and choose "Junk > Junk E-mail Options" (same approach to block senders without having emails from them).
- Select the "Blocked Senders" tab and click "Add".
- Enter a full email address ("user@example.com"), a domain ("@example.com"
, or a subdomain ("@sales.example.com"), or using a wildcard to block all subdomains ("@*.example.com"). Click "OK" to add the entry to your blocked list. 
- You can also block emails by country: select the "International" tab and click "Block Top-Level Domain List" to block certain email domains (regardless of senders' physical location).
- Click "Blocked Encoding List" to block senders based on language setting on their computer and/or the language used in messages they send (regardless of location or email domain).
- Click "OK" to save your preferences and return to Outlook.
- Emails from blocked senders or blocked domains go to the spam folder ("Junk E-mail"). To make Outlook automatically delete these messages (not recommended), right-click on a email, choose "Junk > Junk E-mail Options", and check the "Permanently delete suspected junk e-mail instead of moving it to the Junk E-mail folder" checkbox in the "Options" tab.
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