I too have a very common firstname.lastname@example.org. For personal emails, I just reply and let them know they've got the wrong falloutboy. One guy, a screenwriter in LA, gave my address to a lot of his family, so I had to have kind of an awkward exchange with his mother and one of his aunts who CONTINUES to send me photos of her young son. This is weird stuff I don't want in my inbox.
For the DirecTV emails, I submitted like 15 messages to their general customer service inquiry form. That took like four months to get completely cleared up.
Once I got looped in on an email thread where the other three people were high school kids using Facebook, so my only method for actually communicating was that I had to add as a friend a high school girl. I'm a 30 year old man. My wife was less than thrilled.