Open the message from the sender you wish to block
Click the More icon then select Block Senders. Note: The More icon is the three dots to the right of Spam.
In the Block senders dialog, confirm that you wish to block the sender(s) by selecting Block all future emails and clicking the OK button. Note: You can also select to Delete all existing emails from the sender(s).
You can also manually add email addresses to your blocked list in the Security and privacy pane in Settings.
Block email addresses in Settings in Full-featured Mail
In the Security and privacy pane, click the trash can icon next to the email address you wish to unblock. You'll see a Blocked sender deleted confirmation message.
From the pull-down menu on the top-right, select Settings then click the Go button.
On the left, select Blocked Addresses.
Under Blocked addresses, enter an email address you wish to block then click the Add button. Note: You can block up to 1,000 email addresses. The blocked email address will appear under Blocked addresses.
From the pull-down menu on the top-right, select Settings then click the Go button.
On the left, select Blocked Addresses.
Under Blocked addresses, click the trash can icon next to the email address you wish to unblock. The email address will immediately be removed from the blocked address list.
