How to block annoying and unknown emails from a person or domain?

Flagging emails spam is the method most of the people use to get rid of the unknown emails. When the time moves on, spam folder would be filled up and make your email account load little slower than usual. You would start cursing your ISP assuming that the speed of the internet is reduced. Why to go through all this? You can block annoying emails from unknown persons or sources from receiving by simple methods provided by the email providers. Let's see how annoying, unknown emails can be blocked for different email providers.

Blocking Emails in Gmail

• Login to your Gmail account.
• Find the 'Wrench' icon at the top right corner. Go to 'Settings'.
• Click on the 'Filters' tab.
• You'll notice 'Create a new filter' option. Click on it.

• Enter the email address(s) you don't want to get emails from in the 'From' field. For Eg., you can give email like as username@example.com or you can type a syntax *@example.com to block emails from entire domain.
• You can also block emails based on the list of keywords that you can specify and Subject, attachment of the email that you would receive along with. 

Blocking Emails in Yahoo

• Login to your Yahoo account.
• Find the 'Wrench' icon on the top right corner and hover mouse pointer on it.
• Click on 'Settings' from the hovered menu options.
• Go to 'Blocked Addresses'. Add the email address you don't want to receive email from. For Eg., Type username@example.com and click 'Block' button. Then the email address is added to the blocked list emails. Note: Yahoo doesn't accept any syntaxes in this field.

• If you want to enter a syntax to block emails from, click on 'Filters' and you will find options to add syntaxes, Subject and Body content.

Blocking Emails in Outlook

• Login to your Outlook account.
• Find a 'Wrench' icon at the top right of the screen. Click on it.
• Click on 'More Mail Settings' from the dropped down options.
• Among the several categories of options, find 'Preventing Junk Mail' category of options.

• Click on 'Filters and Reporting' settings.

• Choose the highlighted options according to your needs. In the 'Block content from unknown senders' options, you can opt out to block attachments from unknown senders. 
• Click on 'Save' when you are done with filtering.
• Now come back to options categories.
• Click on 'Safe and Blocked Senders' options.

• Add emails or syntaxes by clicking on the 'Safe Senders'. Some email ID would be already added based on their reputation. You can remove them if wanted.

• Now come back to 'Safe and Blocked Senders' options. The other two options 'Safe Mailing Lists' and 'Blocked Senders' are also look the similar. You can add emails you wanted to block in 'Blocked Senders' category and add personal emails in the 'Safe Mailing Lists'. 
• The only difference between the 'Safe Senders' and 'Safe mailing Lists' is that the second list of emails won't be having any suggestions from the outlook team. It is full personalized section of allowing emails.

Note: The above screenshots resembles the present interfaces of the respective email providers. The user interface may be changed in future to cope up with 'that day technologies'.