someone else's address on TO: line


New Email
Some of the emails I receive have a specific email address (not mine) listed on the TO: line. Specifically this one:
My email address is nothing like this one. Mine is and a different name altogether. The other email address shows up on all different kinds of emails I receive. Some are personal emails where someone has written me a personal note, so I know the email is meant for me (even though it looks as if it was sent to this other email address), and it also shows up on mailing list emails (that I am subscribed to) where it was sent from a company to a list of people.
My email address isn't even on the email, just the other one. How am I receiving those emails and why is someone else's address on the TO: line?
What's going on?