@Oliroe wrote:
Dropbox forces me to change my password due to a so-called password leak. For this, I need an old email address I don't have access to.
You can try contacting Support, but without access to the email account you may not be able to gain access to the Dropbox account. You need to maintain an active email address on your account so you can receive password resets and one-time security codes used during sign in.
To contact Support, visit the Support page while you're NOT signed in to a Dropbox account, including these forums, and you'll see an option for sign in issues. It's best to use an Incognito or Private browsing session to make sure you're not signed in.