This question already has an answer here:
I have an old Steam account with a really old email address. Steam wants to send me an account verification code due to my PC being replaced and upgraded since I created the account. My PC changes have also made my old Outlook email inaccessible. Outlook needs to know the emails I sent and what content they contained, but I never sent any emails via that email address. Thus, I cannot recover my old account. I tried clicking the Settings option on my Steam browser, but nothing happened. Is there any possible way I could access my old Steam account and regain access to the games I have?