I Cant access an old email address thats tied to my account and it wont let me change anything with my account without logging into it

I have an old email that i cannot access due to me being gone for the army and it being cancled due to not logging into it for too long and when im trying to access my xbox live account and manage my account it asks for the security code for my primary email and then sends me to log into that email address that i have no access too and have no password for anymore. i would like to take the old email off my account so i will be able to use my primary email as the only one and be able to make changes to my account on xbox live. How can i do this ?