How do I block email from another yahoo user?

How do I block email from "nobody": no sender, no subject?

• I'm getting email from nobody. There's no sender and no subject. It comes in blank. There's no way I'm going to open it, but I right clicked to view the header so I could get the return path. That is given as a number. User name is given as nobody. I cannot block email that has no return path. I have to enter a valid email address into Mail Options. There is no option when I right click on it either, to block it that way. So how would I do that? Also I'd like to know how Yahoo could let such an email through in the first place. If there's not a valid email address to block it, they should not have accepted it. Any help would be appreciated.

• Answer:

  It's Spam mail---pure and simple---so treat it as you would Spam. Trying to block Spam is a colossal waste of time---(even when you have a name and/or address). It's ineffective because Spammers change their addresses with "each" batch they send out and never reuse an old one, so they slip easily past any blocks you can make. By the time Spam mail gets to your inbox (or the spam folder) they have already abandoned that address and moved on to a new address. Blocking an abandoned address is useless. Just click the Spam tag on them, and let Yahoo deal with them---which they do by sending them to the Spam folder (instead of the inbox) and deleting them at preset times.