How to Block Emails From Undisclosed RecipientsIn Feburary 2016 18,

In Feburary 2016 18,
Launch Microsoft Outlook.
Open the undisclosed recipients email. Look at the 'From' field of the email header. Make a note of the domain name portion of the sender's email address. The domain name is the part of the email address which follows the @ symbol. For instance, in the mock email address spam@example.com, 'example.com' is the domain name.
Go to the 'Home' tab. Click 'Junk' then select 'Junk E-mail' options.
Click 'Add' on the 'Block Senders' tab.
Enter the domain name used by the undisclosed recipient email in the provided field box.
Click 'OK.'
Block Emails Addressed to 'Undisclosed Recipients' in Gmail
Log into you Gmail account.
Click the 'Create a filter' link (next to the 'Search the Web' button). The 'Create a filter' dialog box will open.
Enter 'Undisclosed recipients' in the 'To' field. Click 'Next Step.'
Select 'Delete It.' Click 'Create Filter.'
Block Email from Known Spam Domain in Gmail
Open the 'Create a filter' dialog box.
Enter the domain name used by the undisclosed recipient email in the 'From' field box. Click 'Next Step.'
Select 'Delete It' Click 'Create Filter.'
Block Emails Addressed to 'Undisclosed Recipients' Yahoo Mail
Log into your Yahoo Mail account.
Click 'Options' in the upper right corner of the window. Select 'More Options.' In the left-side window panel, select 'Filter.' Click 'New Filter.' The 'Filters' dialog box will open.
Type 'Undisclosed Recipients' in the 'Filter name' field box and the 'Recipients' field box.
Select 'Trash' from the 'Move to Folder' drop-down menu. Click 'Save Changes.'
Block Email from Known Spam Domain in Yahoo Mail
Open the 'Filters' dialog box.
Enter a name for the filter you're creating in the 'Filter name' box.
Type the domain name used by the undisclosed recipient email in the 'Sender' field box. Select 'Trash' from the 'Move to Folder' drop-down menu. Click 'Save Changes.'
In Feburary 2016 18,