I have an email account at yahoo with a username something like my first name but with letters replaced by numbers, so it’s like ma44h3w@yahoo.com, for example.
Today I received a (spam) email at that address, but yahoo lists the “sent to” address as [myrealfirstname.myreallastname]@yahoo.com.
How in hell did the spammers find out my real name? And how did an email that was sent to [myrealfirstname.myreallastname]@yahoo.com find its way to ma44h3w@yahoo.com? 
Shit just got personal.
My niece just got out of Yahoo because Yahoo had let so many addresses be compromised. The hackers were actually sending mail from her account. Of course when they use your own name, you are bound to open it. In her case all the mail was trying to get people to an online shopping site, not do any software damage. Every so often it would send a spam message to everyone in her address book including her and me. I tested the account by placing a new fake address in her address book and the next day they sent a message to that new address. So they were using the account in real time as opposed to stealing the addresses and using them thereafter.
If your full unedited name is within the Yahoo account anywhere, this may be the case with you.