You need to know the email address or email domain in order that you or the spam system can block it.
If you are getting emails with blank addresses you should log onto your email account then tick the box to the left hand side if the "blank" email in the list and then click on the "More" button in the menu bar at the top of the email list. Scroll down the drop down box and click on "View Source".
This should open a page that show you all the information about the email. Look through that information and you should fine numerous reference to the email address that sent you the email.
Once you have that information you need then click on your username at the top right hand side then select "Settings" then click on "Mail" in the left hand column and select "Blocked Senders".
The Blocked Senders list will open. In the email box click "Add" and enter the email address that you found when you search through the source.
Once you have done that you will find that you have just wasted about ten minutes of your life because Spammers are constantly changing their sending email address and domain and as a result it is pointless trying to block them.
When they arrive in your email account, if there is no email address it is certainly a spam email so you are best just to delete it. Do not open it to see if it is a genuine email because all you are doing is alerting the spammer that they have found an active email account and more spam is bound to follow..
