Someone else has the exact same email address as me

My email address is [Edit: Personal Information] someone else has the exact same address as me.  I talked to a company yesterday because they weren't accepting my email address and they said they had someone else's information for that email address.  I occasionally get emails for this person from other companies, I have had this email address since the 90's.  How is this even possible?  Since it's impossible to get a human being on the phone when calling support, I'm trying this.  

Thank you,

[Edit: Personal Information]